Presumptive GOP presidential nominee Mitt Romney responded to further questions about his tax returns today, telling reporters he paid at least 13 percent in taxes in each year of the past decade.

Romney took aim at Senate Majority Leader Harry Reid, calling on the Nevada Democrat to disclose the source behind his claim that Romney did not pay any income taxes for 10 years.

“I paid taxes every single year. Harry Reid’s charge is totally false,” Romney said. “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, by the way.”

Romney told reporters in Greer, S.C., that he reviewed his own returns after the repeated questions from Democrats.

“Over the past 10 years, I never paid less than 13 percent. I think the most recent year is 13.6 or something like that,” Romney said.

Reid spokesman Adam Jentleson expressed skepticism about Romney’s figures.

“We’ll believe it when we see it. Until Mitt Romney releases his tax returns, Americans will continue to wonder what he’s hiding,” Jentleson said in a statement. “Romney seems to think he plays by a different set of rules than every other presidential candidate for the last 30 years, all of whom lived up to the standard of transparency set by Mitt Romney’s father and released their tax returns.”

In an interview that is scheduled to air tonight on NBC, Ann Romney, the wife of the presumed Republican nominee, insisted that no additional returns would be released. She said giving out additional tax returns would give Democrats “more ammunition” to go after her husband.