Romney says he paid at least 13 percent in federal taxes every year

Mitt Romney told reporters on Thursday that he paid at least 13 percent in federal income taxes each of the last 10 years.

“I did go back and look at my taxes and over the past 10 years I never paid less than 13 percent,” Romney said to reporters at a press availability in South Carolina, according to a pool report. “I think the most recent year is 13.6 or something like that, so I paid taxes every single year.”

Romney has released his 2010 returns and an estimate for 2011, which showed he paid just under 14 percent. Romney’s income was predominantly from capital gains, which is taxed at a lower rate than income.

The Republican candidate's taxes came under new scrutiny after Senate Majority Leader Harry Reid's (D-Nev.) charged on the Senate floor earlier this month that an anonymous source had told him the Romneys had avoided paying federal income taxes for a decade.

“Harry Reid’s charge is totally false,” Romney said on Thursday. “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. But every year I’ve paid at least 13 percent and if you add in addition the amount that goes to charity, why the number gets well above 20 percent.”

Ann Romney said in an interview set to air Thursday that "there's nothing we're hiding" in regards to her and her husband's personal finances, and insisted again the campaign had no plans to release additional tax return details.

The Obama campaign shot back that there is "substantial reason to doubt" Romney's claim.

“Mitt Romney today said that he did indeed ‘go back and look’ at his tax returns and that he never paid less than 13% in taxes in any year over the past decade," spokeswoman Lis Smith said in a statement. "Since there is substantial reason to doubt his claims, we have a simple message for him: prove it."

Smith also said Romney has "forfeited the right to have us take him just at his word,” and used the opportunity to rehash earlier Obama campaign attacks over Romney's wealth and business investments while at Bain Capital, the private equity firm he founded.

"Even though he’s invested millions in foreign tax havens, offshore shell corporations, and a Swiss bank account, he’s still asking the American people to trust him," she said. "However, given Mitt Romney's secrecy about his returns, coupled with the revelations in just the one return we have seen to date and the inconsistencies between this one return and his other financial disclosures, he has forfeited the right to have us take him just at his word."

— This story was updated at 1:36 p.m.