The Federal Reserve's massive stimulus program had little impact on the U.S. economy besides weakening the dollar and helping U.S. exports, Federal Reserve Governor Alan Greenspan told CNBC Thursday.

In a blunt critique of his successor, Fed Chairman Ben Bernanke, Greenspan said the $2 trillion in quantative easing over the past two years had done little to loosen credit and boost the economy.

"There is no evidence that huge inflow of money into the system basically worked," Greenspan said in a live interview.

"It obviously had some effect on the exchange rate and the exchange rate was a critical issue in export expansion," he said. "Aside from that, I am ill-aware of anything that really worked. Not only QE2 but QE1."

Greenspan’s comments came as the Fed ended the second installment of its bond-buying program, known as QE2, after spending $600 billion. There were no hints of any more monetary easing—or QE3—to come.

Greenspan said he "would be surprised if there was a QE3" because it would "continue erosion of the dollar."

The former Fed chairman himself has been widely criticized for the low-interest rate policy in the early and mid 2000s that many believe led to the 2008 credit crisis.

Bernanke, who took over for Greenspan in 2006, began implementing the quantitative easing program in 2009 in an attempt to unfreeze credit and prevent a collapse of the US financial system. The strategy has gotten mixed reviews so far.