Senate Majority Leader Harry Reid's office isn't backing down from its charges Mitt Romney may have not paid taxes over the years and demanding he release a decades worth or returns – despite Romney's assertion Thursday that he's paid at least 13 percent in taxes over the last decade.

"We'll believe it when we see it. Until Mitt Romney releases his tax returns, Americans will continue to wonder what he's hiding. Romney seems to think he plays by a different set of rules than every other presidential candidate for the last thirty years, all of whom lived up to the standard of transparency set by Mitt Romney's father and released their tax returns," Reid spokesman Adam Jentleson told Buzzfeed in a statement Thursday.

The comments came in response to Romney's statement earlier in the day Thursday in which he said he has paid at least 13 percent in taxes for the last 10 years and took at shot at the Democratic leader.

"I paid taxes every single year. Harry Reid's charge is totally false. I'm sure waiting for Harry to put up who it was that told him what he says they told him. I don't believe it for a minute," Romney told reporters.

Reid late last month claimed an unidentified investor in Romney's former company Bain had informed him the reason the GOP presidential hopeful had not released more than two years worth of tax returns was because he had not in fact paid taxes for years.

Reid's claim angered the Romney campaign, which has vehemently denounced it as false for weeks. But Reid's statement also forced the issue back to the forefront of the campaign, derailing attempts by Republicans to return the focus to President Barack Obama's record and to the economy generally.