<PAGE>

                                                                    EXHIBIT 10.3

                               PLEDGE AGREEMENT

     THIS PLEDGE AGREEMENT, dated as of December 4, 2001, made by Laidlaw
Holdings, Inc., a Delaware corporation (the "Borrower"), to Third Security, LLC,
a Virginia limited liability company (the "Lender"), recites and provides:

                                    RECITALS
                                    --------

     WHEREAS, pursuant to the letter of intent (the "LOI"), dated as of
December 3, 2001, between Laidlaw Global Corporation, a Delaware corporation and
parent of the Pledgor (the "Borrower"), and the Lender, the Lender has agreed to
make a loan (the "Loan") in the amount of $1,500,000 to the Borrower for the
purposes described in the LOI, such Loan to be evidenced by a secured
convertible note (the "Note") of the Borrower payable to the order of the Lender
as provided in the Note;

     WHEREAS, pursuant to the LOI Borrower and Lender have agreed to execute and
deliver a call and put option agreement (the "Call and Put Option Agreement"),
dated as of the date hereof, which provides that in the event that the Lender
exercises its put rights thereunder, then the consideration for the shares
subject to such put rights shall increase the outstanding principal amount of
the Note and shall be secured by this Pledge Agreement; and

     WHEREAS, the Lender is willing to make the Loan and to execute the Call and
Put Option Agreement but only upon the condition, among others, that the Pledgor
executes and delivers to the Lender this Pledge Agreement;

     NOW, THEREFORE, in consideration of the premises and of the mutual
covenants herein contained and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

                                   AGREEMENT
                                   ---------

     1.   Defined Terms.  For the purposes of this Pledge Agreement, the
          -------------
following terms shall have the following meanings:

          "Event of Default" shall have the meaning assigned to such term in the
           ----------------
     Note.

          "Maturity Date" shall have the meaning assigned to such term in the
           -------------
     Note.

          "Obligations" means (a) all obligations of the Borrower hereunder, and
           -----------
     (b) all indebtedness, liabilities and obligations of the Pledgor or the
     Borrower to the Lender, whether now existing or hereafter incurred, direct
     or indirect, absolute or contingent, secured or unsecured, matured or
     unmatured, joint or several, whether for principal, interest, fees,
     expenses or otherwise.
<PAGE>

          "Pledged Assets" means the Pledged Securities, together with all
           --------------
     certificates, options, rights, dividends, other distributions or intangible
     rights or assets issued as an addition to, in substitution or in exchange
     for, or on account of, any such Pledged Securities, and all proceeds of all
     of the foregoing, now or hereafter owned or acquired by the Pledgor.

          "Pledged Securities" means the capital securities described in
           ------------------
     Schedule 1 hereto and all other capital securities now or hereafter
     ----------
     included in the Pledged Assets.

          "UCC" means the uniform commercial code as adopted by the State of New
           ---
     York.

     2.   Grant of Security Interest.
          --------------------------

          (a) As collateral security for the prompt and complete payment and
performance when due of all of the Obligations and in order to induce the Lender
to enter into the Call and Put Option Agreement and make the Loan in accordance
with the terms thereof, the Pledgor hereby pledges to the Lender the Pledged
Assets and grants to the Lender a lien on and security interest therein.

          (b) If the Pledgor shall become entitled to receive or shall receive,
in connection with any of the Pledged Securities, any:

              (i) Certificate or other evidence of ownership, including, but
without limitation, any certificate representing a stock dividend or in
connection with any increase or reduction of capital, reclassification, merger,
consolidation, sale of assets, combination, stock split, spin-off or split-off;

              (ii) Option, warrant, or right, whether as an addition to or in
substitution or in exchange for any of the Pledged Securities, or otherwise;

              (iii) Dividend or distribution payable in property, including
capital securities issued by an issuer other than the issuer of any of the
Pledged Securities; or

              (iv) Dividends or distributions of any sort (other than those
permitted to be retained by the Pledgor pursuant to Section 2(d));

then the Pledgor shall accept the same as the agent of the Lender, in trust for
the Lender, and shall deliver them forthwith to the Lender in the exact form
received with, as applicable, the Pledgor's endorsement when necessary, or
appropriate stock powers duly executed in blank, to be held by the Lender,
subject to the terms hereof, as part of the Pledged Assets.

          (c) Prior to the occurrence of an Event of Default, the Pledgor shall
retain all voting rights with respect to the Pledged Securities.

                                      -2-
<PAGE>

          (d) Unless an Event of Default has occurred and is continuing, the
Pledgor shall be entitled, if not prohibited by the Note, to receive for its own
use cash dividends or distributions on the Pledged Securities. Upon the
occurrence of an Event of Default, the Lender may require any such cash
dividends or distributions to be delivered to the Lender as additional security
hereunder or applied toward the satisfaction of the Obligations.

     3.   Remedies, Rights Upon Default.
          -----------------------------

          (a) Upon and after the occurrence of an Event of Default, the Lender
may, without demand of performance or other demand, advertisement, or notice of
any kind (except the notice specified below of time and place of public or
private sale) to or upon the Pledgor or any other person (all of which are, to
the extent permitted by law, hereby expressly waived), forthwith realize upon
the Pledged Assets or any part thereof, and may forthwith, or agree to, sell or
otherwise dispose of and deliver the Pledged Assets or any part thereof or
interest therein, in one or more parcels at public or private sale or sales, at
any exchange, broker's board or at any of the Lender's offices or elsewhere, at
such prices and on such terms as it may deem best, for cash or on credit, or for
future delivery without assumption of any credit risk, with the right to the
Lender or any purchaser to purchase upon any such sale the whole or any part of
the Pledged Assets free of any right or equity of redemption in the Pledgor,
which right or equity is hereby expressly waived and released. Notwithstanding
the foregoing, the Pledgor recognizes that the Lender may be unable to effect a
public sale of all or a part of the Pledged Securities and may be compelled to
resort to one or more private sales to a restricted group of purchasers who will
be obligated to agree, among other things, to acquire such capital securities
for their own account, for investment and not with a view to the distribution or
resale thereof. The Pledgor acknowledges that any such private sales may be at
prices and on terms less favorable to the Lender than those of public sales, and
agrees that the sale of the Pledged Securities does not have to be a public sale
in order to be made in a commercially reasonable manner and that the Lender has
no obligation to delay sale of any such Pledged Securities to permit the issuer
thereof to register it for public sale under the Securities Act.

          (b) The proceeds of any such disposition or other action by the Lender
shall be applied as follows:

              (i)   First, to the costs and expenses incurred in connection
therewith or incidental thereto or to the care or safekeeping of any of the
Pledged Assets or in any way relating to the rights of the Lender hereunder,
including reasonable attorneys' fees and legal expenses;

              (ii)  Second, to the satisfaction of the Obligations;

              (iii) Third, to the payment of any other amounts required by
applicable law; and

              (iv)  Fourth, to the Pledgor to the extent of any surplus
proceeds.

                                      -3-
<PAGE>

          (c) The Lender need not give more than five days' notice of the time
and place of any public sale or of the time after which a private sale may take
place, which notice the Pledgor hereby deems reasonable.

     4.   Representations and Warranties of Pledgor.  The Pledgor represents and
          -----------------------------------------
warrants that:

          (a) It is duly incorporated in good standing as a Delaware
corporation. It has, and has duly exercised, all requisite power and authority
to enter into this Pledge Agreement, to pledge the Pledged Assets for the
purposes described in the recitals to this Pledge Agreement, and to carry out
the transactions contemplated by this Pledge Agreement;

          (b) It is the legal and beneficial owner of all of the Pledged Assets;

          (c) Except as otherwise set forth in Schedule 1 hereto, the Pledged
                                               ----------
Securities constitute all of the issued and outstanding capital securities of
each issuer thereof;

          (d) All of the Pledged Securities have been duly and validly issued,
are fully paid and nonassessable, and all of the Pledged Assets are owned by the
Pledgor free of any pledge, mortgage, hypothecation, lien, charge, encumbrance
or security interest in or on such Pledged Assets or the proceeds thereof,
except for that granted hereunder;

          (e) The execution and delivery of this Pledge Agreement, and the
performance of its terms, will not result in any violation of any provision of
the Organizational Documents of the Pledgor or the applicable issuer of the
Pledged Securities or violate or constitute a default under the terms of any
agreement, indenture or other instrument, license, judgment, decree, order, law,
statute, ordinance or other governmental rule or regulation, applicable to the
Pledgor or any of its property; and

          (f) Upon the delivery of all certificates and instruments evidencing
the Pledged Securities to the Lender or its agent, the registration of the
pledge of the Pledged Securities on the books of the issuer thereof and the
filing of financing statements in the filing office described in Schedule 2
                                                                 ----------
hereto naming the Pledgor as debtor, the Lender as secured party and describing
the Pledged Assets, this Pledge Agreement will create a valid first lien upon
and perfected security interest in the Pledged Assets and the proceeds thereof,
subject to no prior security interest, lien, charge or encumbrance, or agreement
purporting to grant to any third party a security interest in the property or
assets of the Pledgor which would include the Pledged Assets.

          (g) The Pledgor's principal place of business, within the meaning of
the UCC, is listed on Schedule 2 hereto. If any of the Pledged Securities is
                      ----------
uncertificated within the meaning of the UCC, the jurisdiction of the issuer of
such Pledged Securities is listed on Schedule 2 hereto.
                                     ----------

      5.  Covenants of Pledgor
          --------------------

                                      -4-
<PAGE>

          (a) The Pledgor hereby covenants that, until the later of (x) the
Maturity Date and (y) the date that all of the Obligations are satisfied in
full, it will not, without the prior written consent of the Lender:

              (i)   Sell, convey, or otherwise dispose of any of the Pledged
Assets (other than cash distributions permitted to be retained by the Pledgor
pursuant to Section 2(d)) or any interest therein or create, incur, or permit to
exist any pledge, mortgage, lien, charge, encumbrance or security interest
whatsoever in or with respect to any of the Pledged Assets or the proceeds
thereof, other than that created hereby; or

              (ii)  Consent to or approve the issuance of any additional capital
securities in the issuer of the Pledged Securities; or any capital securities
convertible voluntarily by the holder thereof or automatically upon the
occurrence or non-occurrence of any event or condition into, or exchangeable
for, any such capital securities, or any warrants, options, rights, or other
commitments entitling any person to purchase or otherwise acquire any such
capital securities or allow the issuer to take any of the foregoing actions; or

              (iii) Change its name, identity or organizational structure (or
state of incorporation) in any manner that might make any financing or
continuation statement filed hereunder seriously misleading within the meaning
of the UCC (or any other then applicable provision of the UCC) unless the
Pledgor has given the Lender at least 90 days' prior written notice thereof or
has delivered to the Lender acknowledgment copies of UCC financing statements
duly executed and duly filed in each jurisdiction in which UCC filings were
required in order to perfect the security interest granted by this Pledge
Agreement in the Pledged Assets and have taken all action (or made arrangements
to take such action substantially simultaneously with such change if it is
impossible to take such action in advance) necessary or reasonably requested by
the Lender to amend such financing statement or continuation statement so that
it is not seriously misleading; or

              (iv)  Change its jurisdiction of incorporation, place of business
or chief executive office as set forth in Schedule 2 hereto unless it has given
                                          ----------
the Lender at least 90 days' prior written notice thereof or has delivered to
the Lender acknowledgement copies of UCC financing statements duly executed and
filed in each of the filing offices in which UCC filings are required in order
to perfect any of the security interests granted hereunder in the Pledged
Assets; or

              (v)   The Pledgor warrants and will, at its own expense, defend
the Lender's right, title, special property and security interest in and to the
Pledged Assets against the claims of any person, firm, corporation or other
entity.

     6.   Notices Concerning Pledged Assets.  The Pledgor will promptly deliver
          ---------------------------------
to the Lender all written notices, and will promptly give the Lender written
notice of any other notices, received by it with respect to Pledged Assets.

     7.   Further Assurances.  The Pledgor shall at any time, and from time to
          ------------------
time, upon the written request of the Lender, execute and deliver such further
documents and do such further

                                      -5-
<PAGE>

acts and things as the Lender may reasonably request to effect the purposes of
this Pledge Agreement, including, without limitation, delivering to the Lender
upon the occurrence of an Event of Default irrevocable proxies with respect to
the Pledged Securities in form satisfactory to the Lender. Until receipt
thereof, this Pledge Agreement shall constitute the Pledgor's proxy to the
Lender or its nominee to vote all Pledged Securities then registered in the
Pledgor's name in accordance with Section 2(c).

     8.   Termination.  This Pledge Agreement shall terminate on the later of
          -----------
(i) the Maturity Date and (ii) the date that all of the Obligations are
satisfied in full, and the Lender shall deliver to the Borrower, or register a
release for the benefit of the Pledgor, at the Pledgor's expense, such of the
Pledged Assets as shall not have been sold or otherwise applied pursuant to this
Pledge Agreement.

     9.   Limitation on Lender's Duty in Respect of Collateral.  Beyond the
          ----------------------------------------------------
exercise of reasonable care to assure the safe custody of the Pledged Assets
while held hereunder, the Lender shall have no duty or liability to preserve
rights pertaining thereto and shall be relieved of all responsibility for the
Pledged Assets upon surrendering it or tendering surrender of it to the Pledgor.

     10.  Severability.  Any provision of this Pledge Agreement that is
          ------------
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

     11.  No Waiver; Cumulative Remedies.  The Lender shall not, by any act,
          ------------------------------
delay, omission or otherwise, be deemed to have waived any of its rights or
remedies hereunder and no waiver shall be valid unless in writing, signed by the
Lender, and then only to the extent therein set forth. A waiver by the Lender of
any right or remedy hereunder on any one occasion shall not be construed as a
bar to any right or remedy which the Lender would otherwise have had on any
future occasion. No failure to exercise nor any delay in exercising on the part
of the Lender, any right, power or privilege hereunder, shall operate as a
waiver thereof, nor shall any single or partial exercise of any right, power or
privilege hereunder preclude any other or future exercise thereof or the
exercise or any other right, power or privilege. The rights and remedies
hereunder provided are cumulative and may be exercised singly or concurrently,
and are not exclusive of any rights and remedies provided by law. None of the
provisions of this Pledge Agreement may be waived, altered, modified or amended
except by an instrument in writing, duly executed by the Pledgor and the Lender.

     12.  Successors and Assigns; Governing Law.  This Pledge Agreement and all
          -------------------------------------
obligations of the Pledgor hereunder shall be binding upon the successors and
assigns of the Pledgor, and shall, together with the rights and remedies of the
Lender hereunder, inure to the benefit of the Lender and its successors and
assigns.  This Pledge Agreement shall be governed by, and be construed and
interpreted in accordance with, the laws of the State of New York.

                                      -6-
<PAGE>

     13.  Further Indemnification.  The Pledgor agrees to pay, and to save
          -----------------------
the Lender harmless from, any and all liabilities with respect to, or resulting
from any delay in paying, any and all excise, sales or other taxes which may be
payable or determined to be payable with respect to any of the Pledged Assets or
in connection with any of the transactions contemplated by this Pledge
Agreement.

     14.  Notices.  All notices and other communications under this Pledge
          -------
Agreement shall be in writing, shall be effective when received, and shall in
any event be deemed to have been received on the date of delivery if delivered
personally or by telecopier; on the second business day after the business day
of deposit with the U.S. Postal Service for delivery by first class mail,
registered or certified, postage prepaid; or on the first business day after the
business day of deposit with a courier for overnight delivery, freight prepaid;
in each such case, addressed as follows (until any such address is changed by
notice duly given):

     To Lender:       Third Security, LLC
                      The Governor Tyler
                      1902 Downey Street
                      Radford, VA 24141
                      Telecopy:  (540) 633-7972
                      Attention: Marcus E. Smith, Esquire

     With a Copy to:  Hunton & Williams
                      Riverfront Plaza, East Tower
                      951 East Byrd Street
                      Richmond, Virginia 23219
                      Telecopy: (804) 344-7999
                      Attention: C. Porter Vaughan, Esq.

     To Borrower
     or Pledgor:      Laidlaw Global Corporation
                      Laidlaw Holdings, Inc.
                      100 Park Avenue
                      New York, New York 10017
                      Telecopy: (212) 949-5139
                      Attention: Mr. Roger Bendelac

     With a Copy to:  Beckman, Millman, Barandes & Douglas, LLP
                      1616 John Street, Suite 1313
                      New York, New York  10038
                      Telecopy: (212) 791-7990
                      Attention: Robert Barandes, Esq.

                                      -7-
<PAGE>

     IN WITNESS WHEREOF, the Pledgor has caused this Pledge Agreement to be duly
executed and delivered as of the date and year first above written.


                              LAIDLAW HOLDINGS, INC.



                              By:  /s/ Roger E. Bendelac
                                   ------------------------------------
                                   Name:  Roger E. Bendelac
                                          -----------------------------
                                   Title: Chairman
                                          -----------------------------

                                      -8-
<PAGE>

                                   Schedule 1
                                   ----------

                               CAPITAL SECURITIES


<TABLE>
<CAPTION>
=========================================================================================
 Issuer, including exact       Certificate No.    No. of Shares      Exact Name of
 name, the type of entity      (if applicable)    or ownership %   Registered Holder
   and jurisdiction of
        organization
-----------------------------------------------------------------------------------------
<S>                           <C>                 <C>             <C>
H&R Acquisition Corp.                100                81%        Laidlaw Holdings, Inc.
-----------------------------------------------------------------------------------------

=========================================================================================
</TABLE>

                                      -9-
<PAGE>

                                   Schedule 2
                                   ----------

                         FILING OFFICES AND INFORMATION



Filing Office:

Delaware Secretary of State


Location of Debtor:

100 Park Avenue
New York, New York 10017

                                      -10-