The Federal Reserve is turning over a record $78.4 billion to the U.S. Treasury Department after its swollen securities portfolios generated big profits in 2010, the central bank said on Monday.

The remittance to the Treasury for 2010 is $31 billion more than a year earlier.

“The increase was due primarily to increased interest income earned on securities holdings during 2010,” the Fed said in a reference to portfolios that have been fattened by buying aimed at stimulating a slow-paced recovery.

The preliminary unaudited results from the Fed showed the 12 federal reserve banks had total estimated 2010 net income of $80.9 billion. Of that, $78.4 billion will flow to the Treasury.

The Fed will issue audited results in the spring.

The U.S. central bank has faced heavy criticism from some lawmakers because of its heavy buying of securities, including government-sponsored enterprise mortgage-backed securities and U.S. Treasury securities.

Fed officials who briefed reporters said asset sales would be part of a so-called “exit strategy” for the Fed in the future, but only once the economy was on a sound footing. That means sales of the securities may be some way down the road, they added.

The Fed turns over profits to the Treasury annually and has never posted a loss. But the central bank took a number of extraordinary actions during and after the 2007-2009 financial crisis that critics say may have left it with some poor-quality holdings in its portfolios.

A Fed official said that if the Fed had to make sales and take some losses, it could always scale back the amount it remits to the Treasury annually. But there is no mechanism in place for it to get past remittances returned by the Treasury.

In testimony to Congress last Friday, Fed Chairman Ben Bernanke gave no sign the Fed was ready start scaling back its bond purchase program. But he also gave no hints about further buying beyond the June deadline for the $600 billion program.