<PAGE>

                                                                    EXHIBIT 2.10

DATED                                                              27 April 2005

            (1)   MITEL NETWORKS LIMITED

            (2)   HIGHBRIDGE INTERNATIONAL LLC (as Security Agent)

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                     CHARGE OVER BOOK DEBTS AND CASH AT BANK
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                                   MORGAN COLE
                                 Bradley Court
                                   Park Place
                                Cardiff CF10 3DP

                                    Ref: MDM

<PAGE>

DATE:                 April 2005

PARTIES:

(1)   MITEL NETWORKS LIMITED, a private company limited by shares incorporated
      in England and Wales under number 1309629 whose registered office is at
      Portskewett, Monmouthshire, NP26 5YR ("COMPANY")

(2)   HIGHBRIDGE INTERNATIONAL LLC ("SECURITY AGENT") as trustee for itself and
      the other Secured Parties.

AGREEMENT

1.    DEFINITIONS AND INTERPRETATION

1.1   DEFINITIONS

      In this Charge unless the context otherwise requires:

      "ACCOUNT" means the Company's current account number        , Canadian
      Dollars account number        , Euro account number        or US Dollar
      account number        (as relevant) all with Barclays Bank Plc, Corporate
      Banking Centre, Wales and the South West, PO Box 1015, 3rd Floor, Windsor
      Court, 3 Windsor Place, Cardiff, Sort Code 20-60-58 as the same may be
      redesignated, re-named, re-numbered or replaced.

      "BORROWER" means Mitel Networks Corporation, a corporation incorporated
      under the laws of Canada.

      "COLLATERAL AGENCY AGREEMENT" means the collateral agency agreement dated
      the date hereof between, among others, the Security Agent, the Borrower
      and the Noteholders (as defined therein);

      "CREDIT BALANCE" means the sum standing to the credit of the Account from
      time to time.

      "DEBTS" means all book debts and other debts now or in the future due or
      owing to the Company and arising in respect of goods sold, leased or for
      services rendered to customers.

      "EDC CHARGE" means the charge over UK book debts and cash at bank dated 3
      March 2003 and granted by the Company to Export Development Canada as
      amended on 11 June 2003.

      "GUARANTEE" means the guarantee entered into by the Company in favour of
      the Security Agent (on behalf of itself and the other Secured Parties)
      dated on or around the date hereof securing all monies, liabilities and
      obligations of the Borrower to the Security Agent and the other Secured
      Parties in connection with the Transaction Documents.

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      "SECURED PARTIES" means the Security Agent and the holders from time to
      time of the Notes and "SECURED PARTY" means any of them.

      "TRANSACTION DOCUMENTS" means the Securities Purchase Agreement among the
      Borrower, the Security Agent and others dated on or about the date hereof,
      the senior secured convertible notes (the "NOTES") issued pursuant
      thereto, the Security Documents (as defined in the Notes), the
      Registration Rights Agreement (as defined in the Notes) and the Collateral
      Agency Agreement.

1.2   INTERPRETATION

            1.2.1 References in this Charge to any enactment shall be deemed to
                  include references to such enactment as re-enacted, amended or
                  extended for the time being.

            1.2.2 Clause headings are for convenience only and shall in no way
                  affect the construction of this Charge.

            1.2.3 Section 61 of the Law of Property Act 1925 shall govern the
                  construction of this Charge.

            1.2.4 References to the "COMPANY", the "SECURITY AGENT" and the
                  "SECURED PARTIES" shall be construed so as to include their
                  respective successors or permitted assignees (whether
                  immediate or derivative).

            1.2.5 References in this Charge to the singular include references
                  to the plural and vice versa).

            1.2.6 Any reference to this Charge or any other document shall, save
                  as otherwise expressly provided herein, be construed as a
                  reference to this Charge or such other document as amended,
                  varied, supplemented, novated and/or replaced in any manner
                  from time to time.

            1.2.7 If any of the provisions of this Charge are or are found to be
                  invalid, illegal or unenforceable in any respect under any
                  law, the validity, legality and enforceability of the
                  remaining provisions shall not in any way be affected or
                  impaired.

2.    COVENANT TO PAY

      The Company covenants on demand to discharge to the Security Agent (for
      the benefit of itself and the other Secured Parties) all of its
      obligations and liabilities under the Guarantee whether:

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                                     - 3 -

2.1   present or future;

2.2   actual or contingent; and/or

2.3   owed by the Company alone or jointly and/or severally with others

(the "SECURED OBLIGATIONS").

3.    CHARGE

3.1   The Company with full title guarantee and as a continuing security charges
      by way of fixed charges with the payment or discharge of all monies,
      obligations and liabilities hereby covenanted to be paid or discharged by
      the Company:

            3.1.1 the Debts; and

            3.1.2 all monies both present and future from time to time standing
                  to the credit of the Account.

3.2   The security from time to time constituted by or pursuant to this Charge
      shall be in addition to and shall not prejudice, determine or affect any
      other security which the Security Agent (for the benefit of itself and the
      other Secured Parties) may from time to time hold for or in respect of all
      or any part of the monies, obligations and liabilities hereby secured. No
      prior security held by the Security Agent (for the benefit of itself and
      the other Secured Parties) over the property charged by this Charge or any
      part of it shall merge in the security created hereby or pursuant hereto
      which will remain in force and effect as a continuing security until
      discharged by the Security Agent (for the benefit of itself and the other
      Secured Parties).

4.    RESTRICTIONS ON DEALING

4.1   The Company shall not without the prior written consent of the Security
      Agent:

            4.1.1 create or permit to subsist any mortgage, charge, pledge,
                  hypothecation, lien (other than a lien arising by operation of
                  law) or other security interest on the Credit Balance or any
                  of the Debts other than this Charge and the EDC Charge;

            4.1.2 sell, discount, factor, lend or otherwise dispose of the whole
                  or any part of the Debts or the Credit Balance other than in
                  accordance with clause 4.2 of this Charge.

4.2   The Company may continue to withdraw monies from the Account until the
      Security Agent gives notice to Barclays Bank Plc in accordance with the
      terms of the Notice contained in Schedule One to this Charge. The Security
      Agent confirms that it will only give such notice following the occurrence
      of an Event of Default (as defined in the Transaction Documents).

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                                     - 4 -

5.    COVENANTS BY THE COMPANY

5.1   The Company shall:

            5.1.1 pay into the Account all monies which it may receive in
                  respect of the Debts and until such payment will hold all such
                  monies on trust for the Security Agent (for the benefit of
                  itself and the other Secured Parties) and shall not without
                  the prior written consent of the Security Agent release, set
                  off, compound or deal with the Debts otherwise than by getting
                  in and realising the same in the ordinary and proper course of
                  its trading business (and for this purpose the realisation of
                  the Debts by means of block discounting, factoring or the like
                  shall not be regarded as dealing in the ordinary and proper
                  course of its trading business);

            5.1.2 pay into the Account all monies which it receives in respect
                  of the Debts prior to this Charge becoming enforceable and any
                  monies received by the Company and paid into such account in
                  respect of the Debts of the Company shall upon such payment in
                  stand released from the fixed charge on the Debts created in
                  this Charge and shall stand subject to the fixed charge
                  created under clause 3.1.2 of this Charge. Any such release
                  will in no respects derogate from the subsistence and
                  continuance of the said fixed charge on all other Debts of the
                  Company for the time being outstanding;

            5.1.3 deal with the Debts in accordance with any directions from
                  time to time given in writing by the Security Agent and in
                  default of and subject to any such directions not release,
                  factor, sell at discount, charge, assign or otherwise deal
                  with the Debts otherwise than by getting in and paying the
                  same into such account which for the avoidance of doubt will
                  not prevent the Company from entering into any arrangements
                  with individual debtors to accept less than the full amount of
                  a Debt where there are commercial reasons for doing so;

            5.1.4 if called upon to do so by the Security Agent execute a legal
                  assignment of the Debts in such form as the Security Agent may
                  require and give notice thereof to the debtors from whom the
                  Debts are owing or Incurred and take such other steps as the
                  Security Agent may require to perfect such legal assignment;

            5.1.5 immediately following the creation of this Charge give notice
                  of this Charge to Barclays Bank Plc in the form contained in
                  Schedule One to this Charge and procure that Barclays Bank Plc
                  acknowledges such notice to the Security Agent substantially
                  in the form contained in Schedule Two to this Charge within 30
                  business days of the date of this Charge.

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                                     - 5 -

6.    ENFORCEMENT

6.1   This Charge shall become enforceable if (i) any of the monies, obligations
      and liabilities secured by this Charge shall not be paid or discharged by
      the Company in accordance with clause 0 of this Charge or (ii) upon the
      occurrence of any Event of Default under the Notes.

6.2   Section 103 of the Law of Property Act 1925 shall not apply and the
      statutory power of sale and all other powers under that or any other Act
      as varied or extended by this Charge shall arise on and be exercisable at
      any time after the Security Agent shall have demanded the payment or
      discharge by the Company of all or any of the monies, obligations and
      liabilities secured by this Charge.

6.3   Section 93 of the Law of Property Act 1925 dealing with the consolidation
      of mortgages shall not apply to this Charge.

7.    RECEIVER'S AND SECURITY AGENT'S POWERS

7.1   At any time after this Charge has become enforceable or if the Company so
      requests in writing the Security Agent may without further notice to the
      Company appoint by writing under hand or under seal any one or more
      persons either singly, jointly, severally or jointly and severally to be a
      receiver or receiver and manager (each a "RECEIVER") of all or any part of
      the property charged by this Charge and either at the time of appointment
      or any time thereafter may fix his or their remuneration and except as
      otherwise required by statute may remove any such Receiver and appoint
      another or others in his or their place.

7.2   Any Receiver shall be the agent of the Company which shall be solely
      responsible for his acts and defaults and the payment of his remuneration.

7.3   Any Receiver shall subject to any liabilities or restrictions expressed in
      the deed or instrument appointing him have all the powers conferred by the
      Law of Property Act 1923 and the Insolvency Act 1986 on mortgagors and
      mortgagees in possession (but without liability as such) receivers and
      administrators appointed under those Acts which in the case of joint
      receivers may be exercised either jointly or severally. In addition, but
      without prejudice to the generality of the foregoing the Receiver shall
      have power (in the name of the Company or otherwise and in such manner and
      on such terms and conditions as he shall think fit where relevant to the
      property in respect of which he is appointed) to:

            7.3.1 take possession of collect and get in all or any part of the
                  property in respect of which he is appointed and for that
                  purpose to take any proceedings;

            7.3.2 carry on or concur in carrying on the business of the Company
                  and to raise money from the Security Agent or others on the
                  security of any property charged by this Charge;

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                                     - 6 -

            7.3.3 sell, assign or otherwise dispose of or concur in selling,
                  assigning, or otherwise disposing of all or any of the Debts;

            7.3.4 make any arrangement or compromise between the Company and any
                  other person which he may think expedient;

            7.3.5 employ, engage and appoint managers and other employees and
                  professional advisers for any of the purposes detailed in this
                  clause 7.3;

            7.3.6 do all such other acts and things as may be considered to be
                  incidental or conducive to any other matters or powers
                  aforesaid or to the realisation of the security constituted by
                  this Charge and which he lawfully may or can do.

7.4   At any time after this Charge shall have become enforceable or if
      requested by the Company the Security Agent may without further notice and
      without first appointing a Receiver exercise all or any of the powers
      conferred on Mortgages by the Law of Property Act 1925 as varied or
      extended by this Charge and all powers, authorities and discretions
      conferred expressly or by implication on any Receiver in this Charge or
      conferred by statute or common law.

8.    APPLICATION OF PROCEEDS

8.1   Any monies received by the Security Agent or any Receiver shall subject to
      the repayment of any claims having priority to the charges created by this
      Charge be applied in the following order but without prejudice to the
      right of the Security Agent to recover any shortfall from the Company

            8.1.1 in the payment of all costs, charges and expenses of and
                  incidental to the appointment of the Receiver and the exercise
                  of all or any of his powers and of all outgoings paid by him;

            8.1.2 in the payment of the Receiver's remuneration;

            8.1.3 in or towards the satisfaction of the monies, obligations and
                  liabilities secured by this Charge in such order as the
                  Security Agent in its absolute discretion thinks fit;

            8.1.4 in payment of the surplus (if any) to the person or persons
                  entitled to it.

9.    PROTECTION OF THIRD PARTIES

      No person dealing with a Receiver or the Security Agent shall be concerned
      to enquire whether any power which he or it is purporting to exercise has
      become exercisable or whether any money is due under this Charge or as to
      the application of any money paid, raised or borrowed or as to the
      propriety or regularity of any sale by or other dealing with such Receiver
      or the Security Agent. All the protection to purchasers contained in

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                                     - 7 -

      Sections 104 and 107 of the Law of Property Act 1925 shall apply to any
      person purchasing from or dealing with a Receiver or the Security Agent.

10.   ENTRY INTO POSSESSION

      If the Security Agent or any Receiver shall enter into possession, of the
      property hereby charged or any part thereof it or he may from time to time
      and at any time go out of such possession. Neither the Security Agent nor
      any Receiver shall in any circumstances (either by reason of any entry
      into or taking of possession of any such property or for any other reason
      and whether as mortgagee in possession or on any other basis) be liable to
      account to the Company for anything except its or his actual receipts or
      be liable to the Company for any loss or damage arising from any
      realisation of the property hereby charged or from any act, default or
      omission in relation thereto.

11.   POWER OF ATTORNEY

      The Company irrevocably appoints the Security Agent, any Receiver and any
      person nominated by the Security Agent jointly and also severally to be
      the attorney of the Company with the power of substitution and in its name
      and otherwise on its behalf and as its act and deed to sign or execute all
      deeds, instruments and documents which the Security Agent or any receiver
      may require or deem proper for any of the purposes of or which the Company
      ought to do under this Charge. The Company agrees to ratify and confirm
      anything such attorney shall lawfully and properly do.

12.   CURRENCY INDEMNITY

      For the purpose of or pending the discharge of any of the monies,
      obligations and liabilities secured by this Charge, the Security Agent may
      convert any monies received, recovered or realised by the Security Agent
      under this Charge (including the proceeds of any previous conversion) from
      their existing currency into such other currency as the Security Agent may
      think fit and any such conversion shall be effected at the banker's then
      prevailing spot selling rate of exchange for such other currency against
      the existing currency. As a separate and independent obligation the
      Company agrees to indemnify and hold harmless the Security Agent against
      any shortfall between any amount received or recovered by it in respect of
      any payment due under this Charge and converted in accordance with the
      clause into the currency in which such amount was payable and the amount
      in such currency which was due and payable to the Security Agent under
      this Charge.

13.   NEW ACCOUNTS

      If the Security Agent shall at any time receive actual or constructive
      notice of any charge or other interest affecting any part of the property
      hereby charged then the Security Agent may open a new account or accounts
      for the Company and if the Security Agent does not do so then the Security
      Agent shall be treated as if it had in fact done so at the time when it
      received or was deemed to receive notice and as from that time all
      payments made by the Company to the Security Agent shall be credited or
      treated as having been credited to

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                                     - 8 -

      the new account and shall not operate to reduce the amount secured by this
      Charge at the time when the Security Agent received or was deemed to have
      received such notice.

14.   FURTHER ASSURANCE

      The Company shall whenever requested by the Security Agent immediately
      execute and sign all such deeds and documents and do all such things as
      the Security Agent may require at the Company's cost in relation to the
      Debts or the Credit Balance for the purpose of perfecting or more
      effectively providing security to the Security Agent for the payment and
      discharge of the monies, obligations and liabilities secured by this
      Charge.

15.   SET-OFF

      The Security Agent may at any time after this Charge has become
      enforceable and without notice to the Company combine or consolidate all
      or any of the Company's then existing accounts with and liabilities to the
      Security Agent and set off or transfer any sum or sums standing to the
      credit of any one or more of such accounts in or towards satisfaction of
      any of the liabilities of the Company to the Security Agent on any other
      account or in any other respects. The Security Agent shall notify the
      Company that such a transfer has been made.

16.   COSTS AND INDEMNITY

16.1  All costs, charges and expenses properly Incurred by the Security Agent in
      relation to this Charge or the monies and liabilities hereby secured shall
      be reimbursed by the Company to the Security Agent on demand on a full
      indemnity basis and until so reimbursed shall carry interest as mentioned
      in the Guarantee from the date of payment to the date of reimbursement and
      be secured on the property charged by this Charge.

16.2  The Security Agent and every Receiver, attorney or other person appointed
      by the Security Agent under this Charge and their respective employees
      shall be entitled to be indemnified on a full indemnity basis out of the
      property charged by this Charge in respect of all liabilities and expenses
      properly incurred by any of them in or directly or indirectly as a result
      of the exercise or purported exercise of any of the powers, authorities or
      discretions vested in them under this Charge and against all actions,
      proceedings, losses, costs, claims and demands in respect of any matter or
      thing done or omitted in any way relating to the property charged by this
      Charge and the Security Agent and any such Receiver may retain and pay all
      sums in respect of the same out of the monies received under the powers
      conferred by this Charge.

17.   MISCELLANEOUS

17.1  The Security Agent may without discharging or in any way affecting the
      security created by this Charge or any remedy of the Security Agent grant
      time or other indulgence or abstain from exercising or enforcing any
      remedies, securities, guarantees or other rights which it may now or in
      the future have from or against the Company and may make any arrangement,
      variation or release with any person or persons without prejudice either
      to

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                                     - 9 -

      this Charge or the liability of the Company for the monies, obligations
      and liabilities secured by this Charge.

17.2  The Security Agent shall have a full and unfettered right to assign the
      whole or any part of the benefit of this Charge and the expression "THE
      SECURITY AGENT" shall include its successors and assigns and the Security
      Agent shall be entitled to disclose any information to any actual or
      prospective assignee successor or participant.

17.3  The provisions of this Charge shall be severable and if at any time any
      one or more such provisions is or becomes invalid, illegal or
      unenforceable the validity, legality and enforceability of the remaining
      provisions shall not in any way be impaired.

17.4  The rights and remedies of the Security Agent provided by this Charge are
      cumulative and are not exclusive of any rights, powers or remedies
      provided by law and may be exercised from time to time and as often as the
      Security Agent may deem expedient.

17.5  Any reference in this Charge to any statute or any section of any statute
      shall be deemed to include reference to any statutory modification or
      re-enactment thereof for the time being in force.

17.6  This Charge may be executed in more than one counterpart each of which
      shall be deemed to constitute an original.

18.   NOTICES

18.1  A demand notice or other communication to the Company in connection with
      this Charge:

            18.1.1 shall be in writing signed by any manager or officer of the
                   Security Agent or of any branch thereof and;

            18.1.2 shall be left at or sent by facsimile or prepaid ordinary
                   post (airmail if posted to a place outside the United
                   Kingdom) to the Company addressed to the person at the
                   address identified with its signature below.

18.2  A demand, notice or other communication shall take effect from the time it
      is received (or if earlier the time it is deemed to be received in
      accordance with clause 18.2) unless a later time is specified in it.

18.3  A letter or facsimile is deemed to be received:

            18.3.1 in the case of a posted letter unless actually received
                   earlier on the second (fifth if posted to a place outside the
                   United Kingdom) day after posting; and

            18.3.2 in the case of facsimile on production of a transmission
                   report from the machine from which the facsimile was sent
                   which indicates that the facsimile was sent in its entirety
                   to the facsimile number of the recipient.

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                                     - 10 -

19.   GOVERNING LAW AND JURISDICTION

19.1  This Charge shall be governed by and construed in accordance with the laws
      of England and Wales.

19.2  The Company irrevocably agrees for the benefit of the Security Agent that
      the courts of England and/or any of the federal or State courts sitting in
      The City of New York, Borough of Manhattan will have jurisdiction to hear
      and determine any suit, action or proceeding, and to settle any disputes
      which may arise out of, or in connection with, this Charge and, for that
      purpose, irrevocably submits to the jurisdiction of such courts.

19.3  The Company irrevocably waives any objection which it might now or
      hereafter have to any of the courts referred to in clause 19.2 being
      nominated as the forum to hear and determine any suit, action or
      proceeding, and to settle any disputes which may arise out of, or in
      connection with, this Charge and agrees not to claim that any such court
      is not a convenient or inappropriate forum.

19.4  The submission to the jurisdiction of the courts referred to in clause
      19.2 will not (and is not to be construed so as to) limit the right of the
      Security Agent to take proceedings against the Company in any other court
      of competent jurisdiction, nor will the taking of proceedings in any one
      or more jurisdictions preclude the taking of proceedings in any other
      jurisdiction, whether concurrently or not.

19.5  The Company hereby consents in respect of any legal action or proceeding
      arising out of, or in connection with, this Charge, to the giving of any
      relief, or the issue of any process in connection with such action or
      proceeding including, without limitation, the making, enforcement or
      execution against any property whatsoever (irrespective of its use or
      intended use) of any order or judgment which may be made or given in such
      action or proceeding.

19.6  To the extent that the Company may in any jurisdiction claim for itself or
      its assets, immunity from suit, execution, attachment (whether in aid of
      execution, before judgment or otherwise) or other legal process and, to
      the extent that in any such jurisdiction there may be attributed to itself
      or its assets such immunity (whether or not claimed), the Company hereby
      irrevocably agrees that it will not claim, and hereby irrevocably waives,
      such immunity to the full extent permitted by the law of such
      jurisdiction.

20.   DELIVERY

      The Company has executed this Charge as a deed on the condition that it
      shall not be created for the purposes of the Companies Act 1985 Section
      395 (as amended) nor delivered for the purposes of Section 36A of that
      Act, until it is dated by or on behalf of the parties.

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                                     - 11 -

21.   AVOIDANCE OF PAYMENTS

      No assurance, security or payment which may be avoided or adjusted under
      any enactment relating to bankruptcy or insolvency or under Part VI of the
      Insolvency Act 1986 or similar legislation binding on the Company in a
      jurisdiction other than England and Wales and no release, settlement or
      discharge given or made by the Security Agent on the faith of any such
      assurance, security or payment shall prejudice or affect the right of the
      Security Agent to recover from the Company (including the right to recover
      any monies which it may have been compelled by due process of law to
      refund under the provisions of the Insolvency Act 1986 and any costs
      payable by it pursuant to or otherwise incurred in connection with such
      process) or to enforce the security created by or pursuant to this Charge
      to the full extent of all moneys and liabilities secured by this Charge.

22.   SECURITY AGENT

      The relevant provisions of the Transaction Documents shall apply to the
      Security Agent's rights, obligations, powers and duties under this Charge
      as if set out in this Charge in full.

23.   REPRESENTATION AND WARRANTY BY THE COMPANY

23.1  The Company hereby represents and warrants to the Security Agent (for the
      benefit of itself and the other Secured Parties) that (other than under
      the EDC Charge) there currently exists no restriction on charging or
      assigning the Debts where such restriction would have a material adverse
      effect on the business, properties or financial condition of the Company
      or the Company's ability to perform its obligations under the Guarantee.

23.2  The Company acknowledges that the Security Agent (for the benefit of
      itself and the other Secured Parties) has accepted this Charge in full
      reliance on the representation and warranty set out in this clause 0,
      notwithstanding any investigation made by or on behalf of the Secured
      Parties. The representation and warranty made by the Company in this
      clause 0 for the benefit of the Secured Parties is material and shall
      survive the execution and delivery of this Charge.

24.   RIGHTS OF THIRD PARTIES

      Save as expressly provided to the contrary in any Transaction Document:

24.1  a person who is not a party to this Charge may not enforce any of its
      terms under the Contracts (Rights of Third Parties) Act 1999; and

24.2  the consent of any third party is not required to rescind, vary, amend or
      terminate this Charge at any time.

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                                     - 12 -

25.   TRUST PROVISIONS

25.1  The Security Agent holds the security constituted by this Charge on trust
      for the Secured Parties in accordance with the provisions of the
      Collateral Agency Agreement.

25.2  The perpetuity period applicable to each trust constituted by this Charge
      shall be eighty years.

26.   TERMINATION

      This Charge is a continuing security, and shall not terminate or be
      discharged until the earlier of (a) performance and indefeasible payment
      in full of all of the Secured Obligations and (b) the date on which a
      Qualified EPO (as defined in the Notes) is consummated.

IN WITNESS whereof the Company has executed this Charge as a Deed and the
Security Agent has executed this Charge the day and year first before written.
<PAGE>

                                  SCHEDULE ONE

                      NOTICE OF CHARGE TO BARCLAYS BANK PLC

                                     DATE: -

Dear Sirs,

MITEL NETWORKS LIMITED - CURRENT ACCOUNT NO.        CANADIAN DOLLARS ACCOUNT NO.
EURO ACCOUNT NO.        AND US DOLLAR ACCOUNT NO.        (THE "ACCOUNT") WITH
YOU

We give you notice that by a charge ("the Charge") dated - April 2005 we have
charged by way of fixed charge to Highbridge International LLC. ("Security
Agent") (as Security Agents for the benefit of itself and the other Secured
Parties (under the Securities Purchase Agreement dated - April 2005 among Mitel
Networks Corporation, as principal debtor, and Security Agent, as amended) all
monies from time to time standing to the credit of the Account.

We irrevocably instruct and authorise you from time to time and at any time
without reference to or further authority from us, and without any enquiry by
you as to the justification for any such matter:

1.    to disclose to Security Agent such information relating to the Account as
      they may request you to disclose, and

2.    following notice from Security Agent that the security constituted by the
      Charge has become enforceable, not to permit the payment out of or the
      withdrawal or transfer from, the Account by us of any sums standing to the
      credit of the Account other than in accordance with the written
      instructions of Security Agent.

These instructions are not to be revoked or varied without the prior written
consent of Security Agent.

This letter is governed by the laws of England and Wales.

Please confirm your agreement to the above by sending the attached
acknowledgement to Security Agent with a copy to ourselves.

Yours faithfully,

___________________________________________
Director
For and on behalf of Mitel Networks Limited

<PAGE>

                                  SCHEDULE TWO

                      ACKNOWLEDGEMENT BY BARCLAYS BANK PLC

<TABLE>
<S>                                              <C>
Highbridge International LLC. as Security Agent  and the Holders from time to time of the
Investment and Corporate Banking                 Notes issued pursuant to the Securities
4th Floor - First Canadian Place                 Purchase Agreement dated the same date as
Toronto                                          the Charge referred to below.
Ontario
Canada M5X 1H3
</TABLE>

Dear Sirs,

MITEL NETWORK LIMITED - CURRENT ACCOUNT NO.        CANADIAN DOLLARS ACCOUNT NO.
EURO ACCOUNT NO.        AND US DOLLAR ACCOUNT NO.        ("THE ACCOUNT")

We acknowledge receipt of a notice of charge ("the Notice") dated - of a charge
in your favour dated - of all monies from time to time standing to the credit of
the Account.

We confirm that:

1.    we accept the instructions and authorisations contained in the Notice;

2.    we have not received notice of any right or interest of any third party in
      the Account, the sums standing to the credit of the Account or the debt
      represented by the Account;

3.    we have neither claimed or exercised nor will claim or exercise any
      security interest, set-off, counterclaim or other rights in respect of
      the Account, the sums standing to the credit of the Account or the debt
      represented by the Account.

We are aware that you are relying on this letter in connection with your rights
under the above-mentioned charge.

This letter is governed by the laws of England and Wales.

Yours faithfully,

______________________________________
Duly authorised officer
For and on behalf of Barclays Bank Plc

<PAGE>

      IN WITNESS whereof the Company has executed this Charge as a Deed and the
Security Agent has executed this Charge the day and year first before written.

EXECUTED as a Deed (but not delivered          }
until the date hereof by MITEL                 }
NETWORKS LIMITED and signed by                 }
two directors or a director and the secretary  }

                                           Director /s/ [ILLEGIBLE]
                                                    ------------------------

                                           Director /s/ Paul Butcher
                                                    ------------------------
NOTICE DETAILS

       Address: Mitel Business Park
                Portskewett
                Caldicot
                Gwent NP26 5YR

SIGNED by HIGHBRIDGE                    }         HIGHBRIDGE INTERNATIONAL LLC
INTERNATIONAL LLC BY:                   }
HIGHBRIDGE CAPITAL                      }        BY: HIGHBRIDGE CAPITAL
MANAGEMENT, LLC                         }        MANAGEMENT, LLC
for and on behalf of Security Agent     }

                                            By:  _______________________________
                                                  Name: Ari J. Storch
                                                  Title: Managing Director

<PAGE>

      IN WITNESS whereof the Company has executed this Charge as a Deed and the
Security Agent has executed this Charge the day and year first before written,

EXECUTED as a Deed (but not delivered          }
until the date hereof by MITEL                 }
NETWORKS LIMITED and signed by                 }
two directors or a director and the secretary  }

                                           Director ______________________

                                           Director/Secretary ____________

NOTICE DETAILS

       Address: Mitel Business Park
                Portskewett
                Caldicot
                Gwent NP26 5YR

SIGNED by HIGHBRIDGE                  }          HIGHBRIDGE INTERNATIONAL LLC
INTERNATIONAL LLC By:                 }
HIGHBRIDGE CAPITAL                    }          By: HIGHBRIDGE CAPITAL
MANAGEMENT, LLC                       }          MANAGEMENT, LLC
for and on behalf of Security Agent   }

                                             By: /s/ Adam J. Chill
                                                 -------------------------------
                                                 Name: Adam J. Chill
                                                 Title: Managing Director