Herb Allison, the head of the government's $700 billion financial bailout program, said Wednesday morning that he is leaving the Treasury Department at month's end.

In a letter to his colleagues in U.S. Treasury's Office of Financial Stability, Allison said that the Troubled Asset Relief Program (TARP) has proven to be remarkably successful in achieving its goal of stabilizing the nation's financial system and laying the groundwork for an economic recovery.

In the spring of 2009 President Obama nominated Allison, then serving as Fannie Mae's CEO, to oversee the TARP. His official title was assistant Treasury secretary for financial stability and counselor to Treasury Secretary Timothy Geithner. He also served as a White House adviser on policy matters.

Allison said he is stepping down to return to Connecticut. He will be succeeded on an interim basis by Tim Massad, who is chief counsel and chief reporting officer for TARP.

Massad will take the post effective Sept. 30. Before joining government, Massad was a partner for 17 years at the New York law firm of Cravath, Swaine & Moore.

The $700 billion bailout program was created by Congress in October 2008 at the height of the financial crisis. The TARP  cannot commit money to new programs as of Oct. 3, although it will continue to support existing programs.

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