WASHINGTON — Federal Reserve Governor Frederic Mishkin will leave at the end of August and return to teaching at Columbia University, the central bank announced Wednesday. His departure means yet another empty seat on the Fed as it battles housing, credit and financial debacles.

Mishkin, who been on the Fed board since Sept. 5, 2006, submitted his resignation to President Bush. His exit would leave the Fed with just four of its seven board seats filled.

"Rick's contributions to the intellectual underpinnings of monetary policy at the Federal Reserve have been invaluable," said Fed Chairman Ben Bernanke. "His keen insights, deep analysis and humor have enriched our deliberations."

Mishkin, 57, will return to Columbia University's Graduate School of Business as a professor of economics and resume teaching in the fall, the Fed said.

The Fed's meeting on Aug. 5 will be Mishkin's last.

His departure comes as the Fed has been working urgently to help the economy recover from the blows of the housing slump, a painful credit crunch and financial turmoil. The Fed, beginning last September, has carried out its most aggressive rate-cutting campaign in two decades to brace the wobbly economy. It also has taken a number of unconventional steps to help banks and investment houses overcome credit problems and help ease stresses in financial markets.

President Bush has nominated people to the two Fed board seats currently open, but the Senate hasn't moved forward on confirmation proceedings.