Add hedge fund star, Stanley Druckenmiller, now CEO of Duquesne Family Office, to those who believe the Federal Reserve is behind the curve in withdrawing its massive stimulus.

The Fed has kept its federal funds rate target at a record low of zero to 0.25 percent since December 2008. And its balance sheet has bulged to a record $4.4 trillion through quantitative easing.

"I hope we can all agree that once-in-a-century emergency measures are no longer necessary five years into an economic recovery," Druckenmiller, a former colleague of hedge fund legend George Soros, said at a New York investment conference, CNBC.com reports.

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"Today's Fed policy seems not only unnecessary but fraught with unappreciated risk," said Druckenmiller, who has studied central bank policies for decades, made billions with bets on currencies and interest rates and averaged annual compounded investment returns of 30 percent.

Druckenmiller said he worried that the Fed's easy-money policies would have negative consequences. "I really hope I am wrong in my assessment, I really do ... The problem is the Fed is making a bet from which their adjustment could be way too late and have significant adverse consequences," he said.

"There is a heated debate as to what a 'neutral' funds rate would be. We should be debating why we haven't moved more meaningfully toward the neutral funds rate, if for no other reason than so the Fed will have additional weapons available if the outlook darkens again."

The neutral fed funds rate historically has been 4 percent, but some analysts, such as Pimco's Bill Gross, say it will now be 2 percent.

Druckenmiller isn't the only one with criticism of the Fed. Stanford University economist John Taylor says it needs to adopt a rules-based monetary policy to help the economy.

"When monetary policy became more rules-based during the 1980s, 1990s and until recently, the economy improved and we got what economists call the Great Moderation of strong economic growth with declining unemployment and inflation," he writes in The Wall Street Journal.

"When policy became more ad hoc, interventionist and discretionary during the past decade, the economy deteriorated, and we got a financial crisis, a Great Recession, and a not-so-great recovery."

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