Paul DeRosa Appointed to Ambac Board of Directors

Ambac Financial Group, Inc. (NYSE: ABK) (Ambac) announced today that Paul DeRosa, a principal of Mt. Lucas Management Corporation, a hedge fund management firm located in Princeton, New Jersey, has joined its Board of Directors effective July 7, 2008. The addition of Mr. DeRosa to the Ambac Board increases its membership to seven. Of the seven, other than the Chief Executive Officer, all are non-employee directors. Commenting on the appointment, Ambac President and Chief Executive Officer, Michael Callen, stated, "The addition of Mr. DeRosa to our Board further enhances its depth and expertise. His skills will be particularly valuable to Ambac at this time. I’ve known Paul for over 30 years and I look forward to working with him on the challenges facing Ambac.” During the past 30 years, Mr. DeRosa has served in a variety of positions, starting as a research economist at the Federal Reserve Bank of New York. In 1975, he joined Citibank NA., where he was responsible for developing Citibank’s business in financial derivatives in the early 1980’s and was also the head of the bank’s proprietary bond trading. In addition to his line responsibilities, Mr. DeRosa authored Citibank’s interest rate risk management system, which subsequently became the model for the system adopted by the BIS. Mr. DeRosa then co-founded Eastbridge Capital Inc., a bond trading company and primary dealer in United Treasury bonds, becoming CEO of the holding company in 1995. He joined Mt. Lucas in 1998. Mr. DeRosa holds a PhD from Columbia University and is the author of several books and articles on subjects in economics. 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 guarantor of public finance and structured finance obligations, has earned a Aa3 rating from Moody's Investors Service, Inc. and a AA rating from Standard & Poor's Ratings Services; Moody’s rating is on negative outlook while Standard & Poor's maintains a credit watch negative. Ambac Financial Group, Inc. common stock is listed on the New York Stock Exchange (ticker symbol ABK).