Senate Majority Leader Harry Reid's credibility is being questioned after he charged that Mitt Romney didn't pay taxes for 10 years.

Reid made the accusation this week during a wide-ranging interview with The Huffington Post blog site. He claimed a former investor in Romney's Bain Capital company gave him the information.

"Harry, he didn't pay any taxes for 10 years," Reid recalled the person saying.

"Now, do I know that that's true? Well, I'm not certain," Reid continued. "But obviously he can't release those tax returns. How would it look?"

The comments have generated a lot of controversy.

Now, The Washington Post "Fact Checker" has given Reid "four Pinocchios" for his claim, since he refused to reveal his source.

Romney has only released two years of tax returns, but denies Reid's claim.

The Washington Post had a team of experts look at Romney's history of income and investments, and determined that his portfolio "is not structured to yield zero taxes."

Still, Reid and other Democrats aren't backing down from the accusation.

Romney said he has no plans to release any more tax returns.