Summarize the following court judgment. ivil Appeal Nos. 622625 of 1982. From the Judgment and Order dated 14.1.82 of the Allaha bad High Court in W.P. Nos. 3387/79	 3327	 2829/80 and 747/81. Shobha Dixit	 section Markandeya	 M.N. Shroff	 Anil Kumar Gupta. A.K. Sanghi	 V.J. Francis	 P.D. Sharma	 A.K. Panda	 Sunil Kumar Jain and R.B. Mehrotra for the appearing par ties. The Judgment of the Court was delivered by B.C. RAY	 J. These appeals by special leave are against the common judgment and order dated 14.1.1982 quashing the seniority list in the cadre of Assistant Engineers in the United Provinces (Buildings & Roads Branch) Class II pre pared on 29.7.1980 and 18.12.1980 with 19.12.1980. A writ of mandamus was also issued to the State Government for prepa ration of fresh seniority list in respect of Assistant Engineers in the Civil Engineering Wing and Electrical and Mechanical Wing respectively in accordance with the guide lines mentioned in the said judgment. The facts giving rise to these writ petitions are in brief as follows: Previously Public Health Department as well as the Irrigation Department of the Government of Uttar Pradesh were integrated into Public Works Department comprising both these two branches. In 434 1922 Irrigation branch was separated into a different inde pendent department. Similarly	 in 1927 Public Health Depart ment was separated. In 1936 U.P. Service of Engineers Class II Rules (Buildings and Roads Branch) pertaining to P.W.D. were framed in exercise of powers conferred under the Gov ernment of India Act. Identical rules also governed the Irrigation Department. Before entering into the controversy that has been raised in the instant appeal it is appropriate to refer to the relevant provisions of the said rules. Rule 3(b) defines 'Member of the Service ' as a Government servant appointed in substantive capacity	 under the provisions of these rules or of rules in force previous to the introduc tion in the cadres of the service. Clause (c) defines 'Direct recruitment ' or 'Direct appointment ' as recruitment or appointment in the manner prescribed in rule 5(i)	 (ii) and (iii) of these rules. In Rule 4 which is captioned as `Strength of Cadre ' it is mentioned in clause (ii) of the said rule that the Government may increase the cadre by creating permanent or temporary posts from time to time as may be found necessary. Rule 5 lays down five sources of recruitment: (i) by direct appointment from amongst engineer students who have passed out of Thomson Civil Engineering College	 Roorkee	 and who have completed a course of training in the Buildings and Roads Branch as engineer students after consulting the Public Service Commission; (ii) by the appointment after (sic) advertisement and after consulting the Public Service Commission; (iii) by the appointment of officers in the temporary service of the United Provinces Public Works Department	 Buildings and Roads Branch	 after consulting the Public Service Commission; provided that it will not be necessary to consult the Commission in the case of appointment of a temporary officer to a permanent vacancy if he has already been appointed to a temporary post in the cadre of service after consultation with the Commission. (iv) by promotion of members of the United Provinces Subordinate Engineering Service in the Public Works Department	 Buildings and Roads Branch	 who have shown exceptional merits; (v) by promotion of computers in the Public Works Depart 435 ment	 Buildings and Roads Branch	 who have shown exceptional merit and who are technically qualified. It has been specifically provided in Rule 6 that the Government will decide in each 'case the source from which a vacancy shall be filled up provided that 25% of the vacan cies shall be reserved for selected qualified members of the Subordinate Engineering Service and Computers. It thus provides that barring 25% of the vacancies to be filled by promotion from Engineering Subordinate Services and Comput ers	 the remaining 75% of the vacancies are to be filled up by direct recruitment as provided in sub clause (ii) and (iii) of Rule 5. Rule 17 which is termed as 'Probation ' specifically provides that all persons appointed to the service	 who are not already in the permanent employ of the Buildings and Roads Branch of the United Provinces Government	 shall be placed on probation for four years	 provided that such of them as have undergone training as engineer students	 or have served as temporary engineers in the Buildings .and Roads Branch of the United Provinces Government	 may be permitted to count the period of such training and service	 respectively towards this period of probation. Rule 19 deals with confirmation of probationers. It mentions that a probationer shall be confirmed in his ap pointment after he has completed the prescribed period of probation	 has passed all the tests prescribed in the rules and the Government is satisfied that he is fit for confirma tion. It also provides therein that all confirmations under this rule shall be notified in the United Provinces Gazette. Rule 23 states that seniority in the service shall be determined according to the date of order of appointment to it provided that if the order of appointment of two or more candidates bears the same date	 their seniority inter se shall be determined according to the order in which their appointment has been notified. On December 7	 1961 an office memorandum No. 4162 EBR XXIII PWD 90 EBR 1954 was issued by the Government laying down the principles for recruitment to the permanent and temporary posts. It is stated therein that in future direct recruitment to both permanent and temporary vacancies of Assistant Engineers (Civil	 Electrical and Mechanical) in the Public Works	 Irrigation and Local Self Government Engineering Departments	 will be made on the results of competitive examination to be conducted by the Public Serv ice Commis 436 sion. Candidates possessing technical and other qualifica tions prescribed in the rules for the Uttar Pradesh Service of Engineers in the Departments concerned will be eligible to appear at the examination for that particular service. It has been further provided therein that successful candidates in order of merit will be appointed on probation against vacant permanent posts and those following will be appointed against temporary posts. It also lays down the manner of filling up the vacancies in the permanent cadre of the service of Assistant Engineers in the Irrigation Department as well as in the PWD Department. In PWD Department 50% of the vacancies in the permanent cadre will be filled up through competitive examination	 25% by promotion from amongst overseers and computers and 25% by selection from amongst temporary Assistant Engineers recruited through the Commission. It has been further provided that as a measure of concession to the existing temporary Assistant Engineers who were recruited as temporary Assistant Engineers on the advice of the Public Service Commission prior to the intro duction of this scheme	 the distribution of vacancies in the permanent cadre of Assistant Engineers will be 25% by direct recruitment through competitive examination; 25% by promo tion from subordinate service and 50% by selection from amongst existing temporary Assistant Engineers. It has also been provided that the Government may in consultation with the Public Service Commission increase or decrease the percentage fixed for recruitment by selection and competi tive examination in any particular year. In para 7 of the said memorandum it has been provided that temporary and officiating Assistant Engineers possessing the requisite technical qualifications will be eligible to appear in the competitive examinations and the maximum age limit in the case of those working in the department with the approval of the Commission	 or after having been recruited by the Com mission will be 40 years. Thereafter on 28.7.1969 an amendment to the Rule was made by the Government in exercise of power under proviso to Article 309 of the Constitution. This is known as the United Provinces Service of Engineers (Buildings and Roads Branch)	 Class II (Amendment) Rules	 1969. These rules shall be deemed to have been in force since March	 1962. The relevant provisions of these Rules are quoted hereinbelow: Rule 3: In these rules unless there is anything repugnant in the subject or context: (a) The 'Service ' means the U.P. Service of Engineers (Build 437 ings and Roads Branch)	 Class II	 (b) 'Member of the Service ' means a government servant appointed in a substantive capacity	 under the provisions of these rules or of rules in force previous to the introduc tion of these rules to a post in the cadre of the service. (c) 'Direct recruitment ' or 'Direct appointment ' means recruitment or appointment in the manner prescribed in rule (5)(a) (i) and 5(b)(1); (d) 'Commission ' means the Uttar Pradesh Public Service Commission; (e) 'Department ' means the Public Works Department	 Uttar Pradesh; (f) 'Governor ' means the Governor of Uttar Pradesh. (g) 'Secretary ' means the Secretary to Government Public Works Department	 Uttar Pradesh; (h) 'Chief Engineer ' means the Chief Engineer	 Public Works Department	 Uttar Pradesh. (i) 'Period of recruitment ' means the period upto the end of December in the calendar year succeeding year in which the recruitment or selection is made; (j) 'Citizen of India ' means a person who is or is seemed to be citizen of India under Part II of the Constitution of India; (k) 'Government means the Government of Uttar Pradesh. Rule 5: Source of recruitment: Recruitment to the post of Assistant Engineer shall be made from the following sources (a) in permanent vacancies (i) by direct recruitment on the result of a competitive examination conducted by the Commission; 438 (ii) by selection from amongst the Officers appointed as Assistant Engineer by direct recruitment through the Commission and working in temporary or officiating vacancies in the department; (iii) by promotion of members of the Public Works Department	 Subordinate Engineering Service and the Public Works Department 'Computers ' Service. (b) in officiating or temporary vacancies (i) by direct recruitment on the result of a competitive examination conducted by the Commission; (ii) by promotion of members of the Public Works Department	 Subordinate Engineering Service	 and Public Works Department Computers Service. Rule 6: Number to be recruited from each source The Governor shall decide the number of appointments to be made at each selection in each kind of post from the sources speci fied in rule 5: Provided that recruitment in substantive vacancies occurring during a period of recruitment in the post of Assistant Engineer	 shall	 so far as may be possible	 be made from the source mentioned in rule 5(a) in the following proportion: (a) Fifty per cent of the vacancies shall be filled by direct recruitment on the results for a competitive examination under rule 5(a)(i); (b) Twenty five per cent of the vacancies shall be filled from the source specified in rule 5(a)(ii). (c) Twenty five per cent of the vacancies shall be filled from the source specified in rule 5(a)(iii) which shall be shared by members of the Public Works Department Subordinate Engineering Service and the Public Works Department Computers ' Service in approximate proportion of permanent strength of their respective cadres at the time of selection: Provided further that with a view to giving facility to tempor 439 ary Assistant Engineers recruited in the Department in consultation with the Commission up to the date Commencement of the first competitive examination in accordance with these rules	 the proportion of vacancies to be filled from the three sources mentioned in the first proviso shall be 25 per cent	 50 per cent and 25 per cent respectively subject to review at the discretion of the Government in consultation with the Commission. Explanation The vacancies from the source mentioned in rule 5(a)(ii) will	 until further orders	 be filled from amongst those temporary Assistant Engineers only who were recruited in the Department in consultation with the Commission and were working in this capacity on the date of commencement of first competitive examination: Provided also that recruitment to temporary or officiating vacancies in the posts of Assistant Engineers by promotion from the source mentioned in rule 5(b)(ii) shall be made up to 25 per cent of the vacancies	 occurring during any one period of recruitment in the same proportion as in clause (c) of the first proviso and the remaining vacancies shall be filled by direct recruitment under rule 5(b)(i). NOTE The distribution of vacancies in the permanent cadre in the above manner will be subject to the condition that the Governor	 in consultation with the Commission may	 for special reasons	 increase or decrease the percentage fixed for recruitment by selection and competitive examination in any particular period of recruitment. On November 26	 1971 a further amendment to the U.P. Service of Engineers (Buildings and Roads Branch)	 Class II Rules has been brought in and these rules are called U.P. Service of Engineers (Buildings and Roads Branch) Class II (Amendment) Rules	 1971. Rule 23 which deals with seniority has been substituted. The relevant portion of Rule 23 is quoted hereunder: "Except as provided for hereunder seniority in the service will be determined by the date of order of appointment in a substantive vacancy . . . . . . On the basis of these amended rules of 1969 and 1971 exami na 440 tions were held and the successful candidates in the said examinations were appointed to the permanent posts and they were placed on probation. These appointees were called direct recruits in short 'D ' category. The petitioner Nos. 1	 2 and 4 who are appellants here in these appeals are those direct recruits. The appellant Nos. 1 and 2 who were working in the PWD as temporary Assistant Engineers after selection by the Commission were successful in 1962 competi tion for appointment against permanent posts. The Appellant No. 3 who was also working as temporary Assistant Engineer in the PWD after selection by the Public Service Commission in 1962 also competed in the examination held in 1964 for appointment against a permanent post. The appellant No. 4 who was working in the Irrigation Department after selection by the Commission in 1962 was successful for appointment against one of the permanent posts in PWD through 1964 competitive examination. It may be mentioned in this connec tion that the first competitive examination was held in 1962 on the basis of the memorandum dated December 7	 1961. The next examination was held in 1964. Similar examinations were held thereafter till 1971 in accordance with the amended Rules. The Shukla Committee in para 36 of its report ob served that "the System had done more harm than good to the Service" and ultimately recommended that in future such direct recruitment for permanent posts should be discontin ued. No examinations were held in 1963. After 1971 the recruitment by this method was discontinued by executive instructions issued in 1972 vide Office Memorandum dated 23.6.1972 (Annexure C2 to the counter affidavit of S.C. Gupta dated 23.1.81 in Writ Petition No. 3327 of 1980 Syed Masood Tagi Zaidi vs State of U.P. ) This was followed by another order dated 8.6. 1973 (Annexure C 3 ibid) stopping direct promotion against permanent vacancies. These deci sions were taken on the basis of the recommendations of Shukla Committee 's Report. The respondents are the directly recruited Assistant Civil Engineers in the Buildings and Roads Branch pursuant to the provisions of Rule 5(a)(ii) in the temporary posts of the cadre upto 1961 after consultation with the Public Service Commission. These temporary Assistant Engineers who are working continuously since the date of their appointment in the cadre of Assistant Engineers have questioned the seniority list of Assistant Engineers made by the Government in 1980 pursuant to the Office Memorandum dated December 7	 1961 and U.P. Engineering Service (Amendment) Rules of 1969 and 1971 on the grounds that they are arbitrary and discrim inatory being violative of Articles 14 and 16 of the Consti tution. These amended rules have been challenged further on the ground that these 441 rules adversely affect their service conditions and as such prayed for quashing of the seniority list and for determina tion of their seniority on the basis of the decision ren dered by this Court in Baleshwar Dass & Ors. vs State of U. P. & Ors. 	 [1981] 1 SCR 449 on the basis of the length of their continuous service since the date of their becoming member of the service in accordance with the provisions of the 1936 rules. The High Court of Allahabad allowed these Writ Petitions and quashed the 1980 seniority list directing to prepare a seniority list after taking the appointments of officers to the service after selection by Public Service Commission to be substantive appointments to the cadre. Against this judgment and order the above appeals on special leave have been preferred to this Court. The only question that falls for consideration is the determination of seniority of Assistant Engineers in the cadre of the service within the meaning of Rule 3(b) of U.P. Service of Engineers (Buildings and Roads Branch) Class II (Amendment) Rules. It appears that a similar question about the yard stick for determination of seniority between the Assistant Engineers appointed substantively to temporary posts of the cadre and those Assistant Engineers appointed against the permanent posts on probation and confirmed in the said post	 came up for consideration before this Court in Civil Appeal No. 1717 of 1981. In that appeal we have already considered this aspect of the case and relying on the decision in Baleshwar Dass & Ors. vs State of U.P & Ors. and N.K. Chau han & Ors. vs State of Gujarat & Ors. ; 	 we have held that since the cadre of the service of engineers consists of both temporary and permanent posts and as such there can be substantive appointments against tempo rary posts of the cadre in accordance with the provisions of the Service Rules. When a temporary Assistant Engineer is selected and appointed by the Government with the approval of the Public Service Commission after fulfilment of all the tests presented in the said rules	 he shall be deemed to be member of the service and as such the entire length of service from the date of his becoming member of the service has to be reckoned in computing the seniority of the Assist ant Engineers appointed substantively to temporary posts in the service in accordance with the provisions of Rule 23 as it was prior to its amendment by 1971 Rules. We have also held that on the plea of not being confirmed	 the long years of service rendered by an Assistant Engineer though appoint ed to a temporary post substantively cannot be arbitrarily cut off and excluded in determining seniority. 442 Before proceeding to consider the merits of the contro versy raised in this appeal it is pertinent to deal with the preliminary objections raised on behalf of the appellants that the validity of rules of 1969 and 197 1 was not chal lenged by T category officers or by the ad hoc officers at any time prior to the filing of the present writ petitions .out of which the instant appeals on special leave have arisen and as such the writ petitions should be dis missed on the ground of undue delay and laches. This objec tion was elaborately dealt with by the High Court in its judgment ' and it was held that there was no such undue delay and laches which can be considered to be a bar for consider ing the writ petitions. It appears that the seniority list of 1971 that was prepared following 1969 and 1971 rules was challenged by some 'D ' category officers in Civil Writ Petition No. 3734 of 1969 (V. C. Aggarwal vs State of U.P. & Ors.). That petition was allowed and the seniority list of 1971 was quashed. The Government was directed to prepare a fresh seniority list in accordance with law after adjusting the recruitment for the period 1962 to 1966 in accordance with the quota rule. Against that judgment two special appeals were filed being Nos. 634 and 629 of 1972. These appeals were allowed in part. Against that judgment the Government alone came to this Court in SLP(C) No. 951 of 1975. This special leave petition was dismissed on 8.9. Thereafter the impugned list was published in 1980 and it was supplemented on the 18th and 19th December	 1980. In these circumstances we are unable to hold that there has been undue delay and laches on the part of temporary Assist ant Engineers to challenge the aforesaid amended rules and as such there is no merit in this contention. In the instant appeal there is no controversy that all the temporary Assistant Engineers who were appointed in consultation with the Public Service Commission by the Government and bad been rendering their services for long years since 1956 till 1961 when the said notification has been made by the Government have become members of the service in accordance with the provisions of the rules. Therefore on the basis of the provisions of rule 23 as it was before the amendment made in 197 1 these temporary Assistant Engineers are legally entitled to have their seniority reckoned from the date of their being member of the service no matter whether they are holding posts which remain as temporary for years together. It is quite clear that there are about 200 Assistant Engineers who have been appointed substantively by the Government with the approval of the Public Service Commission and as such the direct recruits appointed on the basis of the examination held under the 1969 rules cannot in any manner whatsoever en croach upon the rights of these substantively appointed Assistant Engineers 443 to temporary posts in the matter of determination of their seniority in the said cadre of Assistant Engineers. The Office Memorandum dated December 7	 1961 introduces quotas for filling up vacancies in the cadre of Assistant Engineers in the Public Works Department as well as Irriga tion and Local Self Government Engineering Departments by providing direct recruitment through competitive examination to both permanent and temporary vacancies of Assistant Engineers (Civil	 Electrical and Mechanical). It has been provided therein that the quota of 50% of the vacancies in the cadre of Assistant Engineers in a year will be filled by direct recruits through competitive examination as well as it provides 25% of the permanent posts to be filled up by selection from amongst temporary Assistant Engineers re cruited through the Commission. As a concession however	 it has provided that the quota of direct recruits through competitive examination will be 25% instead of 50% as there are large number of temporary Assistant Engineers from whom the selection can be made to the vacancies in the permanent posts of Assistant Engineers by selection. This memorandum has subsequently been incorporated in the amended rules of U.P. Service of Engineers 1969. In Rule 5 of the said Rules provision has been made for direct recruitment both in permanent vacancies as well as in officiating or temporary vacancies on the basis of competitive examination conducted by the Public Service Commission and the criteria laid down is that those who are more meritorious judged by the result of the examination and occupy higher place will be recruited to the permanent vacancies whereas others less meritorious judged by their performance in the competitive examination will be recruited to the post of officiating or temporary vacancies of Assistant Engineers. It has also been provided therein that the temporary Assistant Engineers already recruited in the department in consultation with the Commis sion will. be permitted to compete in the examination and if they can do well in the competitive examination then they may be appointed in the permanent posts of Assistant Engi neers. This rule if considered properly will clearly show that direct recruits against permanent vacancies on the basis of the competitive examination will score a march over the Assistant Engineers who have been appointed substantive ly in temporary posts of the cadre and have become members of the service. They will be deprived of having their serv ices reckoned from the date of their substantive appointment to temporary posts for the purpose of determination of seniority. In accordance with the provisions of Rule 23 of the amended rules of 1971 which has been substituted for the old rules of 1936 seniority in the service has to be deter mined by the date 444 of order of appointment in a substantive vacancy. As a result this rule expressly debars Assistant Engineers who have been appointed long before the appointment of the direct recruits under the amended rules of 1969 to have their long years of service as Assistant Engineers after being appointed substantively and after being members of the service fulfilling all the tests prescribed within the meaning of rule 3 of the rules of 1936 and also under rule 3(b) as amended by the 1969 amendment to be left out in fixation of seniority. In other words these temporary As sistant Engineers will ever remain temporary though they have been rendering identical service for long years and having same educational qualification and long experience in the service. This memorandum dated 7.12.1961 was considered in Ba leshwar Dass 's case by this Court and it was held that this G.O. was not arbitrary insofar as it fixes the proportion of permanent vacancies to be filled from various sources	 and it has statutory force being under Rule 6. It has also been observed that: "The office memorandum makes it clear that direct recruitments will be made to both permanent and temporary vacancies of Assistant Engineers. But this scheme of 1961 cannot stand in isolation and has to be read as subordinate to the 1936 Rules. After all	 the 196 1 Memorandum cannot override the Rules which are valid under Article 3 13	 and so must be treated as filling the gaps	 not flouting the provisions. " Hence the said O.M. does not affect the petitioners who have become members of the Service and are entitled to have their seniority reckoned from the date of their being members of the Service according to Rule 23 of the 1936 Rules. The 1969 Rules and 197 1 Rules have however	 affected the rights of the respondents who have become members of the Service being substantively appointed in temporary posts as Assistant Engineers inasmuch as there has been an amendment effected in Rule 3(b) by providing that a member of the Service meant a Government servant appointed in a substantive capacity to a post in the cadre of the Service. Rule 3(c) also amends the earlier provisions by meaning direct recruitment as in the manner prescribed in Rule 5(a)(i) and 5(b)(i). Similar amendments have been made in Rule 5 and 6. The effect of these amendments is that Assistant Engineers who have become members of the Service being appointed substantively in temporary posts will no longer be members of the service and will have to wait till they are selected and appointed as Assistant 445 Engineers under Rule 5(a)(ii) against quota fixed by Rule 6 for this purpose. This creates serious prejudice to them and it also creates uncertainty as to when they will be selected and appointed against the quota set up for such selection under Rule 5(a)(ii). The amended Rule 23 lays down that seniority will be determined from the date of order of appointment in substantive vacancy. These amended provisions have been made retrospectively effective from March 1	 1962 to the existing officers i.e. the respondents appointed substantively against temporary vacancies. It has been urged that Government has the power to amend rules retrospectively and such rules are quite valid. Several decisions have been cited of this Court at the Bar. Undoubtedly the Government has got the power under proviso to Article 309 of Constitu tion to make rules and amend the rules giving retrospective effect. Nevertheless	 such retrospective amendments cannot take away the vested rights and the amendments must be reasonable	 not arbitrary or discriminatory violating Arti cles 14 and 16 of the Constitution. "It is well settled that the power to frame rules to regulate the conditions of service under the proviso to article 309 of the Constitution carries with it the power to amend or alter the rules with a retrospective effect: B.S. Vadhera vs Union of India	 ; ; Raj Kumar vs Union of India	 ; K. Nagraj & Ors. vs State of A.P. & Anr. 	 ; and State of J & K vs Triloki Nath Khosla & Ors.	 1. It is equally well settled that any rule which affects the right of a person to be considered for promotion is a condition of service although mere chances of promotion may not be. It may further be stated that an authority competent to lay down qualifica tions for promotion	 is also competent to change the quali fications. The rules defining qualifications and suitability for promotion are conditions of service and they can be changed retrospectively. This rule is however subject to a well recognised principle that the benefits required under the existing rules cannot be taken away by an amendment with retrospective effect	 that is to say	 there is no power to make such a rule under the proviso to article 309 which affects or impairs vested rights. Therefore	 unless it is specifi cally provided in the rules	 the employees who are already promoted before the amendment of the rules	 cannot be re verted and their promotions cannot be recalled. In other words	 such rules laying down qualifications for promotion made with retrospective effect must necessarily satisfy the tests of articles 14 and 16(1) of the Constitution. " The above observations have been made by this Court in the case of T.R. Kapur vs State of Haryana & Ors.	 JT 1986 (SC) 1092 at 1101 446 (in which one of us was a party). It has been held by this Court in E.P. Ravappa vs State of Tamil Nadu	 AIR 1974 (SC) 555 at 583 and Maneka Gandhi vs Union of India	 AIR 1978 (SC) 597 at 624 that there should not be arbitrariness in State action and the State action must ensure fairness and equality of treatment. It is open to judicial review whether any rule or provision of any Act has violated the principles of equality and non arbitrariness and thereby invaded the rights of citizens guaranteed under articles 14 and 16 of the Constitution. As has been stated hereinbefore the Assistant Engineers who have already become members of the Service on being appointed substantively against temporary posts have already acquired the benefit of 1936 rules for having their seniority computed from the date of their becoming members of the Service. 1969 and 197 1 Amended Rules take away this right of these temporary Assistant Engineers by expressly providing that those Assistant Engineers who are selected and appointed in permanent vacancies against 50% quota provided by Rule 6 of the amended 1969 Rules will only be considered for the purpose of computation of seniority from the date of their appointment against permanent vacancies. Therefore the temporary Assistant Engineers are not only deprived of the right that accrued to them in the matter of determination of their seniority but they are driven to a very peculiar position inasmuch as they are to wait until they are selected and appointed against permanent vacancies in the quota set up for this purpose by the amended Rule 6. The direct recruits on the basis of the competitive examina tion conducted by the Commission and appointed against permanent vacancies on probation will supersede the rights that accrued under the unamended rules to the temporary Assistant Engineers having precedences in the matter of determination of their seniority from the date of their appointment against permanent vacancies. In other words	 the Assistant Engineers appointed substantively against tempo rary posts several years before the direct recruits and working in the posts of Assistant Engineers will be pushed down to the direct recruits against permanent vacancies. It is also evident that there are about 200 Assistant Engineers who have been appointed substantively by the Government with the approval of the Public Service Commission before the enforcement of 1969 rules. The direct recruits appointed on the basis of the examination against permanent vacancies will get precedence over Assistant Engineers appointed in the matter of determination of their seniority in the cadre of Assistant Engineers on the basis of changed rules	 par ticularly new Rule 23 which takes into account only appoint ments in substantive vacancies. Thus appointments made under Rule 5(b)(i) are to be treated as temporary i.e. 'T ' catego ry officers and their such services will not be 447 taken into consideration in determining seniority until they are selected and appointed to permanent posts under Rule 5(a)(ii). Note I to Rule 23 made it clear that an appoint ment made substantively on probation against a clear vacancy in a permanent post will be treated as substantive appoint ment. Thus the 1969 and 1971 amendments in effect take away from the officers appointed to the temporary posts in the cadre through Public Service Commission	 i.e. after selec tion by Public Service Commission	 the substantive character of their appointment. These amendments are not only disad vantageous to the future recruits against temporary vacan cies but they were made applicable retrospectively from 1.3.1962 even to existing officers recruited against tempo rary vacancies through Public Service Commission. As has been stated hereinbefore that the Government has power to make retrospective amendments to the Rules but if the Rules purport to take away the vested rights and are arbitrary and not reasonable then such retrospective amendments are sub ject to judicial scrutiny if they have infringed articles 14 and 16 of the Constitution. In the case of S.B. Patwardhan vs State of Maharashtra. ; at 778 Rule 8(iii) of 1960 Rules of Bombay Service of Engineers Grade II which provided that direct recruits on probation in any year will be in a bunch senior to promotees confirmed in that year was declared ultra vires of article 14 of the Constitution as it purported to take away from the promotees their right of seniority being determined from date of their promotion from subordinate service to the posts of Deputy Engineers before confirmation. It was held that: "Though drawn from two different sources~ the direct recruits and promotees constitute in the instant case a single integrated cadre. They discharge identical functions	 bear similar responsibilities and acquire an equal amount of experience in their respective assignments. Yet clause (iii) of r. 8 provides that probationers recruited during any year shall in a bunch be treated as senior to promotees confirmed in that year. This formula gives to the direct recruit even the benefit of his one year period of training and another year 's period of probation for the purposes of seniority and denies to promotees the benefit of their long and valuable experience. If there was some intelligible	 ground for this differentiation bearing nexus with efficiency in public services	 it might perhaps have been possible to sustain such a classification. Instead of adopting an intelligible differentia	 r. 8(iii) leaves seniority to be determined 448 on the sole touchstone of confirmation. Confirmation is one of the inglorious uncertainties of government service depending neither on efficiency of the incumbent nor on the availability of substantive vacancies. " The Office memorandum dated December 7	 196 1 which purports to amend the United Provinces Service of Engineers (Buildings & Roads Branch) Class II Rules	 1936 in our opinion cannot override	 amend or supersede statutory rules. This memorandum is nothing but an administrative order or instruction and as such it cannot amend or supersede the statutory rules by adding something therein as has been observed by this Court in Sant Ram Sharma vs State of Rajas than & Anr.; 	 Moreover the benefits that have been conferred on the temporary Assistant Engineers who have become members of the service after being selected by the Public Service Commission in accordance with the service rules are entitled to have their seniority reckoned in accordance with the provisions of rule 23 as it was then	 from the date of their becoming members of the service	 and this cannot be taken away by giving retrospective effect to the rules of 1969 and 1971 as it is arbitrary	 irrational and not reasonable. We have already mentioned hereinbefore that the amended rules of 1969 read with the amended rules of 197 1 adversely affect the rights of the Assistant Engineers appointed to substantive posts prior to the introduction of these amended rules and create fetters for the long years of service being ever considered for reckoning of seniority in the cadre of Assistant Engineer. It is pertinent to refer in this connec tion the decision of this Court in the case of Mohammad Shujat Ali & Ors. etc. vs Union of India & Ors. etc. ; 	 wherein it has been observed that "it is true that a rule which confers a right of promotion or the right to be considered for promotion is a rule prescribing condition of service." For promotion from Assistant Engineer to the post of Executive Engineer seniority cum merit is the criterion in accordance with the service rules in question. These temporary Assistant Engineers unless they are selected to the 50% quota in permanent vacancies reserved for promo tion from the Assistant Engineers appointed to temporary posts	 will never have their service reckoned for determina tion of seniority in the cadre. It is pertinent to mention in this connection that 'T ' category and 'D ' category engi neers have got some technical qualification i.e. both are graduates in Civil Engineering and both worked as Assistant Engineers in temporary vacancies. the respondents were appointed long before the appointment of appellants as Assistant Engineers in permanent vacancies. The appoint 449 ment of respondents has been made in consultation with the Public Service Commission and according to the decision in Baleshwar Dass 's case the respondents having become members of the Service they are deemed to be appointed substantively in temporary posts. Therefore the amended rules more partic ularly rules 3(c)	 5 and 6 of 1960 rules as well as rule 23 of 197 1 amended rules are wholly arbitrary and discrimina tory and so they are violative of Articles 14 and 16 of the Constitution. It has been tried to be urged in this connec tion on behalf of the direct recruits that the method of selection to the cadre of Assistant Engineers by providing quota for direct recruits in permanent vacancies was intro duced by the authorities concerned in order to attract meritorious and talented engineers in the U.P. Service of Engineers (Buildings & Roads Branch) as there were very little prospects of promotion for such Assistant Engineers to be promoted to the higher posts owing to the large number of Assistant Engineers appointed to temporary posts. It has thus been urged that these new rules have been introduced in order to give an incentive to meritorious and talented engineers to get themselves recruited directly to permanent posts in the cadre on the basis of the competitive examina tion in order to have a fair promotional prospect in the service. This submission cannot be sustained in view of the fact that firstly it seriously prejudices the rights of the Assistant Engineers appointed substantively to the temporary posts and working as Assistant Engineers for a number of years and discriminates them from having their long years of service after being appointed substantively in temporary posts and being members of the service though the 'D ' cate gory engineers appointed much later in permanent posts will steal a march over them by having their seniority reckoned from the date of their appointment on probation. Secondly	 this process of direct recruitment against permanent vacan cies was discontinued after 1971 and these amended rules were not thereafter taken recourse to in filling up the vacancies in the cadre of Assistant Civil Engineers as it worked injustice and had led to patent discrimination vio lating Articles 14 and 16 of the Constitution. This is perhaps the reason and rationale which impelled the Shukla Committee to recommend the discontinuance of this practice of giving promotion to direct recruits. Quota and rota are introduced where recruitments to a cadre of Service are made from two or more sources. But in the instant case the quota has been introduced for the first time after their recruit ment for determining seniority in service 'T ' category having become members of the Service already and also there are no different sources of recruitment as both 'D ' and 'T ' category employees are recruited by examination conducted by Commission. Moreover no quota for filling up permanent vacancies has been 450 provided at the initial stage of recruitment but a quota has been made after recruitment at the stage of confirmation. In this connection it is relevant to mention that the quota and rota which was introduced by the 197 1 amendment of Rule 23 cannot be questioned to be arbitrary in as much as when recruitments to a particular service are made from more than one source quota and rota may be introduced con sistent with the equality clause envisaged in Articles 14 and 16 of the constitution. This decision is new well set tled by several decisions of this Court	 the last of these decisions is in the case of Narender Chadha & Ors. vs Union of India & Ors. 	 In the instant case the question is whether by the substitution of rule 23 by the amendment Act of 1971 the long years of service already rendered by the temporary Assistant Engineers who have become members of the cadre of the service of Assistant Engineers fulfilling all the conditions can be arbitrarily and unreasonably excluded while fixing seniority and 'T ' category officers can be deprived of their long years of services being rackoned for determination of seniority. It has been urged on behalf of the appellants that the classification made between temporary Assistant Engineers though working for a considerable period of time but not appointed against permanent vacancies and direct recruits appointed on the basis of the examination against permanent vacancies on probation is based on merits. In support of this submission the decision in State of Jammu & Kashmir vs Triloki Nath Khosa & 'Ors.	 has been cited at the bar. This decision in our considered opinion is not applicable to the instant case inasmuch as in that case recruitment to the cadre of Assistant Engineers in Jammu & Kashmir Engineering Service was made by direct recruitment of degree holders in civil engineering as well as by trans fer of degree or diploma holders having served as Supervisor for a period of not less than five years. The recruitment rules also further provided for promotion to the cadre of Executive Engineer on the basis of merit	 ability and previ ous service record of the candidates. In 1970 the Jammu & Kashmir Engineering (Gazetted) Service Recruitment Rules 1970 were made providing that recruitment to the post of Executive Engineers was to be made only by promotion of Assistant Engineers possessing degree in civil engineering. It was held by this Court that the classification made had reasonable nexus for classification namely to achieve admin istrative efficiency in the engineering service by introduc ing higher qualification for promotion to the post of Execu tive Engineer. In the instant case	 all the Assistant Engi neers whether appointed in a temporary post of the cadre or in the perma 451 nent post of the cadre are recruited directly from Graduates in Civil Engineering. The only difference is that due to exigencies of service a large number of Assistant Engineers were recruited by the Government in consultation with the Public Service Commission in accordance with Rule 5(a)(ii) of 1936 Rules as it was prior to its amendment	 against temporary vacancies and those Engineers have been working as Assistant Engineers since their appointment from 1956 on wards till the end of 1961 when the impugned 1961 Memorandum was promulgated by the Government and thereafter the amended Rules of 1969 and 197 1 were made. It was for the first time that the amendment in the rules was made retrospective by introducing the process of selecting Assistant Engineers to be appointed directly against permanent posts on probation through examination to be conducted by the Public Service Commission in 1962. Necessary amendments were also made in the Rules 3(c)	 5 and 6 of the 1969 Rules as well as Rule 23 of the 1971 Rules in order to provide better prospects of promotion to these direct recruits by laying down that their seniority will be reckoned from the date of their appoint ment on probation whereas in the case of Assistant Engineers who were working for years together but appointed against temporary posts	 their seniority from the date of their appointment after consultation with the Public Service Commission cannot be counted for the purposes of determina tion of seniority unless they are appointed against perma nent posts and confirmed. Therefore it cannot be said that higher education qualification has been prescribed as in the case of State of Jammu & Kashmir vs Triloki Nath Khosa & Ors. for the purpose of appointing Assistant Engineers directly against permanent post on promotion. In the instant case undoubtedly	 both 'T ' and 'D ' category Assistant Engi neers are Graduates in Engineering and both are performing the same nature of work. It is also significant to note in this connection that the appellants were previously appoint ed as Assistant Engineers against temporary vacancies of the cadre but subsequently on the basis of this examination they have been appointed directly on probation against permanent vacancies. There is nothing to show that these Assistant Engineers had shown any extraordinary or brilliant perform ance as Assistant Engineers. It is also to be noted that the temporary Assistant Engineers have acquired much experience in their work having been appointed much before the direct recruits against permanent vacancies. As stated hereinbefore that under the 1936 Rules the Assistant Engineers appointed against temporary vacancies became members of the Service under the then Rule 3 and they were eligible for their seniority being reckoned from the date of their becoming member of the Service. In these circumstances it is evident that the impugned 452 Rules of 1969 and 197 1 purport to take away or to cruelly cut off the long years of valuable service rendered by these respondents i.e. Assistant Engineers appointed in temporary vacancies of the cadre only to the pretext of appointment against permanent post and confirmation. The effect of the 1969 and 1971 amendments was thus to take away from the officers appointed to the temporary cadre through Public Service Commission i.e. after the selection by the Commis sion the long years of service after becoming members of the Service. It is also pertinent to mention here that though these temporary posts of the cadre have been continuing for over years together yet these temporary posts have not been made permanent before 1961 and thereby depriving the Assist ant Engineers from being appointed against permanent vacan cies even though they have become members of the service being appointed in a substantive capacity. These temporary	 Assistant Engineers after introduction of the amended rules have been relegated to a very uncertain position as to when they will be selected against permanent vacancies by the Commission in the 50% quota provided under Rule 6 of the amended Rules to become members of Service and to have their seniority reckoned. Moreover the fate of those Assistant Engineers who are selected and appointed in temporary posts on the basis of the results of the examination is also very uncertain inasmuch as they will be considered for selection by the Commission against the quota for temporary Assistant Engineers after the Assistant Engineers appointed before them are all considered for selection in the said quota set up for the temporary Assistant Engineers in permanent vacan cies even though they have been appointed through the same process of examination considering all these circumstances we are constraint to hold that the impugned provisions of Rule 3(c)	 5 and 6 of the 1969 Rules and Rule 23 of the 1971 Rules are arbitrary	 irrational an unreasonable infringing Articles 14 and 16 of the Constitution insofar as they affect the question of determining the inter se seniority of temporary Assistant Engineers appointed by the Government i.e. T category officers under rule 5(2) of the Rules as against that of D category officers i.e. officers directly recruited by the Government against permanent vacancies and placed on probation. An argument has been advanced on behalf of the direct recruits i.e. the appellants that they having duly succeeded in the competitive examination on the basis of the amended rules cannot be deprived of their right to be promoted on the basis of the fixation of their seniority in the cadre of Assistant Engineers as provided in the amended rule 23 of 1971 rules. This argument in our considered opinion cannot hold 453 good in as much as the cadre of Assistant Engineers com prises of both permanent and temporary posts. Rule 3(b) specifically lays down that an Assistant Engineer becomes member of the service as soon as he is appointed in the substantive capacity even in a temporary post in the cadre. It is inconceivable how a member of the service can be prevented from having his service reckoned for determination of seniority in the service from the date he became member of the Service. The substituted rule 23 introduced in 197 1 is on the face of it unreasonable and arbitrary in as much as it purports to deprive a member of the service from having his seniority reckoned on the ipse dixit of the rules that he has not been appointed in a substantive vacancy. Rules 3(c) 5 and 6 of 1969 Rules are arbitrary	 irrational and not reasonable infringing Article 14 of the Constitu tion. While considering this we of course agree with the finding arrived at by the High Court that so far as the selections made on the basis of the competitive examination on the basis of the amended rules of 1969 and 197 1 read with G.O. dated 7.12. 196 1 more than two decades before	 should not be disturbed in as much as these selections were not challenged during all these years and these direct recruits have worked there since their appointment. We also make it clear that our decision will not affect any confir mations or substantive promotions made prior to the filing of the writ petitions. It appears that an interim order was made by this Court on 5.5. 1982 to the effect that "if any appointments pursu ant to the fresh rules which are framed	 are made these will be subject to the results of these appeals. " It also appears that in Civil Appeal Nos. 2616 19 of 1981 this Court while disposing of those appeals by order dated 15.4.1981 directed that in regard to promotions already made in accordance with the impugned seniority list there shall be status quo as on the date on which the writ petitions were filed in the court. It was also directed that such promotions and any future promotions made in accordance with the impugned seniority list will abide by the result of these appeals. We make it clear that since we are dismissing these appeals all those ad hoc promotions given during the pendency of these writ petitions as well as civil appeals will not confer any right on the promotees. We further hold that so far as the temporary Assistant Engineers who have been appointed substantively to temporary posts and have been working for years together after being only recruited and selected by the Public Service Commission as required under the service rules have become members of the service but so far as purely ad hoc employees or employ ees on purely officiating basis or employees purely for 454 a temporary period in the cadre of Assistant Engineer in Public Works Department being not members of the service in accordance with the service rules	 are not entitled to have the benefit of their such adventitious	 purely ad hoc and temporary service being not appointed substantively even to a temporary post will not be reckoned for determination of seniority unless and until they become members of the serv ice in accordance with the provisions of service rules. Only those ad hoc appointees whose services have been regularised by the regularisation rules framed under proviso to Article 309 of the Constitution after being duly selected by the Selection Committee and becoming member of the service	 will be entitled to seniority only from the date of order of appointment after selection in accordance with those regula tions as provided in rule 7 of the regulations. We mention in this connection the observations of this Court in the case of Ashok Gulati and Ors. vs R.S. Jain & Ors.	 AIR 1987 (SC) 424 (to which one of us was a party). It has been observed as follows: "According to the accepted canons of service jurisprudence	 seniority of a person appointed must be reckoned from the date he becomes a member of the service . . It is well settled that an ad hoc or fortuitous appointment on a temporary or stop gap basis cannot be taken into account for the purpose of seniority even if the appointee was qualified to hold the post on a regular basis	 as such temporary tenure hardly counts for seniority in any system of service jurisprudence. " Similar observation was also made by this Court in the case of State of Gujarat vs C.G. Desai	 [1974] 2 SCR 255. Therefore we make it clear that the period of service ren dered by the ad hoc appointees before their service has been duly regularised in accordance with the regularisations rules	 cannot be taken into account in reckoning their seniority in service. Their seniority in service will be counted only from the date when such ad hoc appointees after regularisation in accordance with concerned rules have become members of the service. We direct the authorities concerned to prepare a fresh seniority list of all the members of the service in the cadre of Assistant Engineer in the PWD Department on the basis of their length of service from the date they have become members of the service fulfilling all the require ments laid down in the service rules. We cannot but observe in this connection that though the temporary Assistant Engineers have 455 been duly selected by the Public Service Commission after they are appointed as temporary Assistant Engineers yet in spite of several directions given by this Court	 the author ities concerned did not think it fit and proper to prepare the seniority list in accordance with the directions given by this Court and as a result no seniority list in the cadre of Assistant Engineer has yet been prepared following the directions made even by this Court as embodied in the deci sion in Baleshwar Dass & Ors. vs State of U.P. & Ors. On the other hand amendments have been made to the existing 1936 service rules which per se seem to be arbitrary and this led to a spate of litigations. We do hope and expect that con sidering all these	 the Government will take effective steps for preparation of seniority list as early as possible in order to create incentive for the members of the service by holding out prospects of future promotions in the interests of the service. In the premises aforesaid we dismiss these appeals and affirm the judgment and order of the High Court of Allahabad quashing the said seniority list dated 29.7.1980 together with supplementary seniority lists dated 18.12. 1980 and 19.12. 1980 relating to Civil Engineering Wing. Rules 3(c)	 5 and 6 of 1969 Rules as well as Rule 23 of 1971 Rules are also quashed. The condition in Office Memorandum dated 21.1.1980	 Annexure 2 of Writ Petition No. 2447 of 1980 providing that for the selection for the post of Superin tending Engineer the officer must be a confirmed Executive Engineer is quashed. A writ of mandamus be issued directing the Government to prepare a fresh seniority list of Engi neers in the Civil Engineering and E.M. Wing respectively in the light of the observations made hereinbefore. This order	 however	 will not affect any confirmations or promotions (other than ad hoc promotions) made before 29.11.1979. In the facts and circumstances of the case	 there will be no order as to costs. H.L.C. Appeals dis missed.

Rule 3(c) of the U.P. Service of Engineers (Buildings and Roads Branch) Class II Rules	 1936 defined 'direct recruitment ' or 'direct appointment ' as recruitment or appointment of Assistant Engineers in the manner prescribed in r. 5(i)	 (ii) and (iii) thereof	 after consultation with the Public Service Commission. Rule 6 empowered the Govern ment to decide in each case the source from which a vacancy shall be filled up provided that 25% of the vacancies were reserved for promotion of persons selected from subordinate services. Rule 3(b) thereof defined a 'member of the serv ice ' as a government servant appointed in a substantive capacity. Rule 23 stipulated that seniority in the service shall be determined by the date of order of appointment to the service. By an Office Memorandum dated December 7	 1961	 the State Government laid down that direct recruitment to the posts of Assistant Engineers would be made on the results of a competitive examination conducted by the Commission	 the successful candidates being appointed in the order of merit against vacant permanent posts and	 those following	 against temporary posts. It was further laid down that while 50% of the permanent vacancies in the Department would be filled by direct recruitment	 25% of them would be filled by selection from amongst the temporary Assistant Engineers recruited through the Commission and for this purpose the temporary Assistant Engineers already working in the Department who were appointed on the advice of the Commission prior to the introduction of the new scheme and who 428 possessed the requisite qualifications were given relaxation in the age limit upto 40 years for appearing in the competi tive examinations to be conducted by the Commission. As a measure of further concession to the existing temporary Assistant Engineers	 it was provided that initially 50% of the permanent vacancies would be filled up by selection of temporary Assistant Engineers and only 25% thereof would be filled up by direct recruitment. The competitive examina tions were held commencing from the year 1962. On July 28	 1969	 the State Government brought into force the U.P. Service of Engineers (Buildings and Roads Branch) Class II (Amendment) Rules	 1969 with retrospective effect from March	 1962 amending inter alia rr: 3(b)	 3(c)	 5 and 6 of the 1936 Rules to bring them in line with the scheme enunciated in the Office Memorandum dated December 7	 1961. On November 26	 1971	 r. 23 was amended by the U.P. Service of Engineers (Buildings and Roads Branch) Class II (Amendment) Rules	 1971 as under: "Except as provided for hereunder seniority in the service will be determined by the date of order of appointment in a substantive vacancy . " The competitive examinations for direct recruitment of Assistant Engineers in accordance with the new Scheme were held upto the year 1971 and were discontinued by the execu tive instruction contained in Office Memorandum dated June 23	 1972 as it was felt that the system had done more harm than good to the service. The respondents	 who were directly recruited Assistant Engineers appointed	 after consultation with the Commission	 to temporary posts in the cadre upto 1961 challenged the seniority list prepared in 1980 in terms of the Office Memorandum dated December 7	 1961 and the Amendment Rules	 1969 and 1971 as violative of articles 14 and 16 of the Consti tution and prayed for determination of their seniority on the basis of the length of their continuous service in terms of the decision of this Court in Baleshwar Dass & Ors. vs State of U.P. & Ors. 	 [1981] 1 S.C.R. 449. The High Court allowed the petitions and directed preparation of a fresh seniority list by treating the appointments of respondents as substantive appointments to the cadre. The appellants in these appeals were those temporary Assistant Engineers working in the Department who were selected for appointment to permanent vacancies 429 on the results of the competitive examinations held by the Commission. Dismissing the appeal	 this Court	 HELD: There is no controversy that all those Assistant Engineers who were substantively appointed to temporary posts in consultation with the Commission and had been rendering their service for long years till 1961 have become members of the service in accordance with the provisions of the Rules. Therefore	 on the basis of r. 23 as it was before the amendment made in 1971	 these Assistant Engineers are entitled to have their seniority reckoned from the date of their being members of the service	 no matter whether they are holding posts which remain as temporary for years to gether. The direct recruits appointed on the basis of the examination held under the amended Rules cannot encroach upon their rights in the matter of determination of their seniority. [442E H] 2. This Court	 in Baleshwar Dass & Ors. vs State of U. P. & Ors. 	 [1981] 1 S.C.R. 449	 while holding that Office Memorandum dated December 7	 1961 was not arbitrary in so far as it fixed the proportion of permanent vacancies to be filled from various sources	 observed that this scheme of 1961 could not stand in isolation and had to be read as subordinate to the 1936 Rules. Hence	 the aforesaid Office Memorandum does not affect the petitioners who have become members of the service and are entitled to have their sen iority reckoned from the date of their being members of the service in accordance with r. 23 of the 1936 Rules. [440G H; 441A B] 3. The effect of the amendments made in rr. 3(b)	 3(c)	 5 and 6 is that Assistant Engineers who have become members of the Service being appointed substantively in temporary posts will no longer be members of the service and will have to wait till they are selected and appointed as Assistant Engineers under r. 5(a)(ii) against quota fixed by r. 6 for this purpose. This creates serious prejudice to them and it also creates uncertainty as to when they will be selected and appointed against the quota set up for such selection under r. 5(a)(ii). The amended r. 23 lays down that seniori ty will be determined from the date of order of appointment in substantive vacancy. These provisions have been made retrospectively effective from March 1	 1962 to the existing officers i.e.	 the respondents appointed substantively against temporary vacancies. Such retrospective amendments cannot take away the vested rights. [444H; A B] 430 T.R. Kapur vs State of Haryana & Ors.	 JT (1986) S.C. 1092; E.P. Royappa vs State of Tamil Nadu	 A.I.R. 1974 S.C. 555 and Maneka Gandhi vs Union of India	 A.I.R. 1978 S.C. 597; relied on. The Assistant Engineers who have already become members of the service on being appointed substantively against temporary posts have already acquired the benefit of 1936 Rules for having their seniority computed from the date of their becoming members of the service. The Amendment Rules	 1969 and 1971 take away this right of these temporary Assistant Engineers by expressly providing that those As sistant Engineers who are selected and appointed in perma nent vacancies against 50% quota provided by amended r. 6 will only be considered for the purpose of computation of seniority from the date of their appointment against perma nent vacancies. Therefore	 the temporary Assistant Engineers are not only deprived of their seniority but they are driven to a very peculiar position inasmuch as they have to wait until they are selected and appointed against permanent vacancies in the quota set up for this purpose by the amend ed r. 6. There are about 200 Assistant Engineers who have been appointed substantively by the Government with the approval of the Public Service Commission before the en forcement of 1969 Rules. The direct recruits appointed on the basis of the examination against permanent vacancies will get precedence over Assistant Engineers appointed in the matter of determination of their seniority in the cadre of Assistant Engineers on the basis of changed Rules	 par ticularly amended r. 23	 which takes into account only appointments in substantive vacancies. The 1969 and 1971 Amendments in effect take away from the officers appointed to the temporary posts after selection by the Public Service Commission	 the substantive character of their appointment. These amendments are not only disadvantageous to the future recruits against temporary vacancies but they were made applicable retrospectively from March 1	 1962 even to exist ing officers recruited against temporary vacancies through Public Service Commission. The Government has power to make retrospective amendments to the Rules but if the Rules purport to take away the vested rights and are arbitrary and not reasonable then such retrospective amendments are sub ject to judicial scrutiny. [446B H; 447A C] S.B. Patwardhan vs State of Maharashtra	 [1977] 3 S.C.R. 775	 referred to. The Office Memorandum dated December 7	 1961 which purports to amend the U.P. Service of Engineers (Buildings and Roads Branch) Class II Rules	 1936 cannot override	 amend or supersede 431 statutory rules as it is nothing but an administrative order or instruction. The temporary Assistant Engineers who have become members of the service after being selected by the Public Service Commission in accordance with the service rules are entitled to have their seniority reckoned in accordance with the provisions of r. 23 as it was then	 from the date of their becoming members of the service	 and this cannot be taken away by giving retrospective effect to the Amendment Rules of 1969 and 1971 as it is arbitrary	 irra tional and not reasonable. [448B D] Sant Ram Sharma vs State of Rajasthan & Anr.	 ; 	 referred to. The Amendment Rules of 1969 read with the Amendment Rules of 1971 adversely affect the rights of the Assistant Engineers appointed to substantive posts prior to the intro duction of these amended Rules and create fetters for the long years of service being ever considered for reckoning of seniority in the cadre of Assistant Engineers. For promotion from Assistant Engineer to the post of Executive Engineer seniority cum merit is the criterion. These temporary As sistant Engineers	 unless they are selected to the 50% quota in permanent vacancies reserved for promotion from the Assistant Engineers appointed to temporary posts	 will never have their service reckoned for determination of seniority in the cadre. The respondents were appointed long before the appointment of appellants as Assistant Engineers in perma nent vacancies. The appointment of respondents has been made in consultation with the Public Service Commission and according to the decision in Baleshwar Dass 's case the respondent having become members of the Service they are deemed to be appointed substantively in temporary posts. Therefore	 the amended Rules	 more particularly rr. 3(c)	 5 and 6 of 1969 Rules as well as r. 23 of 1971 amended Rules are wholly arbitrary and discriminatory and are violative of articles 14 and 16 of the Constitution. Mohammad Shujat Ali & Ors. vs Union of India & Ors. 	 ; 	 referred to. The argument that the Amendment Rules were framed to attract meritorious and talented engineers in the U.P. Service of Engineers (Buildings and Roads Branch) as there were very little prospects of promotion for such Assistant Engineers to be promoted to the higher posts owing to the large number of Assistant Engineers appointed to temporary posts cannot be sustained	 firstly	 because it 432 seriously prejudices the rights of the Assistant Engineers appointed substantively to the temporary posts and working as Assistant Engineers for a number of years and secondly	 because this process of direct recruitment against permanent vacancies was discontinued after 1971 as it worked injustice and had led to patent discrimination. [449C F] 8. When recruitments to a particular service are made from more than one source	 quota and rota may be introduced consistent with the equality clause envisaged in articles 14 and 16 of the Constitution. In the instant case all the Assistant Engineers whether appointed in a temporary post of the cadre or in the permanent post of the cadre are recruit ed directly from graduates in Civil Engineering. The only difference is that due to exigencies of service a large number of Assistant Engineers were recruited against tempo rary vacancies. Under the 1936 Rules the Assistant Engineers appointed against temporary vacancies became members of the Service under the then r. 3 and they were eligible for their seniority being reckoned from the date of their becoming members of the service. The impugned Rules of 1969 and 1971 purport to take away or to cruelly cut off the long years of valuable service rendered by these Assistant Engineers only on the pretext of appointment against permanent posts. These temporary Assistant Engineers after introduction of the amended Rules have been relegated to a very uncertain posi tion as to when they will be selected against permanent vacancies by the Commission in the 50% quota provided under r. 6 of the amended Rules to become members of service and to have their seniority reckoned. The fate of those Assist ant Engineers who are selected and appointed in temporary posts on the basis of the results of the examination is also very uncertain inasmuch as they will be considered for selection by the Commission against the quota for temporary Assistant Engineers after the Assistant Engineers appointed before them are all considered for selection in the said quota set up for the temporary Assistant Engineers in perma nent vacancies even though they have been appointed through the same process of examination. Considering all these circumstances we are constrained to hold that the impugned rr. 3(c)	 5 and 6 of the 1969 Rules and r. 23 of the 1971 Rules are arbitrary	 irrational and unreasonable infringing articles 14 and 16 of the Constitution. [451G H; 452A F] Narender Chadha vs Union of India & Ors.	 	 referred to. State of Jammu & Kashmir vs Triloki Nath Khosa	 ; 	 distinguished. 433 9. Purely ad hoc employees or employees on purely offi ciating basis or employees purely for a temporary period in the cadre of Assistant Engineer	 being not members of the service in accordance with the service rules	 are not enti tled to have the benefit of their such adventitious	 purely ad hoc and temporary service being reckoned for determina tion of seniority unless and until they become members of the service in accordance with the provisions of service rules. Only those ad hoc appointees whose services have been regularised by the regularisation rules framed under proviso to article 309 of the Constitution after being duly selected by the Selection Committee and becoming members of the Service	 will be entitled to seniority only from the date of order of appointment after selection in accordance with those regula tions as provided in r. 7 of the Regulations. [453H	 454A C] Ashok Gulati and Ors. vs D.S. Jain & Ors.	 ; and State of Gujarat vs C.G. Desai	 [1974] 2 S .C .R. 255	 referred to.