Ambac Financial Group announced that David Wallis has resigned as president and chief executive officer and as a director of Ambac Assurance Corporation. He will remain, however, a director of Ambac Financial. Ambac Financial also announced that Kevin Doyle has resigned as senior vice president and general counsel, effective July 29.

Until their departures, Wallis and Doyle will continue to work to develop and file a plan of reorganization for Ambac Financial before the expiration of its current exclusivity period on July 6.

Neither Wallis nor Doyle offered reason for their resignations, nor did the company list a reason in its Form 8-K filing with the Securities and Exchange Commission. However, the move comes at a time when the company struggles to emerge from bankruptcy (on May 10, Ambac announced $819 million in losses in the first quarter of 2011).

Effective July 30, Stephen Ksenak will succeed Doyle as general counsel. Assuming Wallis' roles as president and CEO, effective as of July 7, will be Diana Adams, senior managing director, as President and CEO, In addition, Adams was appointed as a director of both Ambac Financial and Ambac Assurance, also effective July 7.

Adams, who joined Ambac in 2000, is chief administrative officer with executive responsibility for human resources, technology, and administration. She also is a member of the board of Ambac's UK subsidiary, Ambac Assurance UK Limited, which she chaired from 2008-2010.