Sean Leonard Joins Ambac Financial Group, Inc. as its Chief Financial Officer

Business Wire, June 1, 2005

NEW YORK -- Ambac Financial Group, Inc. (NYSE:ABK) announced that Sean T. Leonard has joined Ambac today as Senior Vice President and Chief Financial Officer. Thomas J. Gandolfo, Ambac's former Chief Financial Officer, will take over responsibility for Ambac's investment and other capital market activities. Those responsibilities include Ambac's global structured credit and Financial Services businesses as well as the investment portfolios.

Mr. Leonard was a Partner with PricewaterhouseCoopers LLP ("PwC"). He has over 18 years of public accounting experience and has been involved with PwC's insurance and capital markets practices over his career. Prior to his admission into the partnership, Mr. Leonard represented PwC on the Financial Accounting Standards Board as a practice fellow where he was actively involved in several financial instrument accounting pronouncements.

Ambac Financial Group, Inc., headquartered in New York City, is a holding company whose affiliates provide financial guarantees and financial services to clients in both the public and private sectors around the world. Ambac's principal operating subsidiary, Ambac Assurance Corporation, a leading guarantor of public finance and structured finance obligations, has earned triple-A ratings, the highest ratings available from Moody's Investors Service, Inc., Standard & Poor's Ratings Services, Fitch, Inc. and Rating and Investment Information, Inc. Ambac Financial Group, Inc. common stock is listed on the New York Stock Exchange (ticker symbol ABK).