Exhibit
      12.1



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CERTIFICATIONS

I, John Edward
    Roberts, certify that:

| | 1. I
        have reviewed this annual report on Form 20-F of United Utilities PLC;                                                                                                                                                                                                                                                                 
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |                                                                                                                                                                                                                                                                                                                                                     
| | 2. Based
        on my knowledge, this report does not contain any untrue statement of
        a material fact oromit
        to state a material fact necessary to make the statements made, in light
        of the circumstances under which such statements were made, not misleading
        with respect to the period covered by this report;
| |                                                                                                                                                                                                                                                                                                                                                     
| | 3. Based
        on my knowledge, the financial statements, and other financial information
        included in this report, fairly present in all material respects the
        financial condition, results of operations and cash flows of the registrant
        as of, and for, the periods presented in this report;                          
| |                                                                                                                                                                                                                                                                                                                                                     

| | 4. The
        registrant's other certifying officer(s) and I are responsible for establishing
        and maintaining disclosure controls and procedures (as defined in Exchange
        Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:                                                                            
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| | 5. The
        registrant's other certifying officer(s) and I have disclosed, based
        on our most recent evaluation of internal control over financial reporting,
        to the registrant's auditors and the audit committee of the registrant's
        board of directors (or persons performing the equivalent functions):

| |  | (a) All
        significant deficiencies and material weaknesses in the design or operation
        of internal control over financial reporting which are reasonably likely
        to adversely affect the registrant's ability to record, process, summarise
        and report financial information; and
| |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  |                                                                                                                                                                                                                                                                                                              
| |  | (b) Any
        fraud, whether or not material, that involves management or other employees
        who have a significant role in the registrant's internal control over
        financial reporting.                                                                                                       



|/s/
          John Edward Roberts | Date
        9 December 2005
|--------------------------------- | ----------------------------
|John Edward
        Roberts,      |                             
|Chief executive                   |                             



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CERTIFICATIONS

I, Simon George
    Batey, certify that:

| | 1. I
        have reviewed this annual report on Form 20-F of United Utilities PLC;                                                                                                                                                                                                                                                                 
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |                                                                                                                                                                                                                                                                                                                                                     
| | 2. Based
        on my knowledge, this report does not contain any untrue statement of
        a material fact oromit
        to state a material fact necessary to make the statements made, in light
        of the circumstances under which such statements were made, not misleading
        with respect to the period covered by this report;
| |                                                                                                                                                                                                                                                                                                                                                     
| | 3. Based
        on my knowledge, the financial statements, and other financial information
        included in this report, fairly present in all material respects the
        financial condition, results of operations and cash flows of the registrant
        as of, and for, the periods presented in this report;                          
| |                                                                                                                                                                                                                                                                                                                                                     

| | 4. The
        registrant's other certifying officer(s) and I are responsible for establishing
        and maintaining disclosure controls and procedures (as defined in Exchange
        Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:                                                                            
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                      
| | 5. The
        registrant's other certifying officer(s) and I have disclosed, based
        on our most recent evaluation of internal control over financial reporting,
        to the registrant's auditors and the audit committee of the registrant's
        board of directors (or persons performing the equivalent functions):

| |  | (a) All
        significant deficiencies and material weaknesses in the design or operation
        of internal control over financial reporting which are reasonably likely
        to adversely affect the registrant's ability to record, process, summarise
        and report financial information; and
| |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  |                                                                                                                                                                                                                                                                                                              
| |  | (b) Any
        fraud, whether or not material, that involves management or other employees
        who have a significant role in the registrant's internal control over
        financial reporting.                                                                                                       



|/s/
          Simon George Batey | Date
        9 December  2005
|-------------------------------- | -----------------------------
|Simon George
        Batey,      |                              
|Group Finance
        Director   |                              



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