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GREER - Mitt Romney said today he has not paid less than a 13 percent taxes during the past ten years. The candidate had told ABC News' David Muir last month that he'd be "happy to go back and look" at his returns.

The tax issue has been a touchy one for Romney and he made clear that he feels there are more important issues on which to concentrate.

"I just have to say given the challenges that America faces 23 million people out of work, Iran about to become nuclear, one out of six Americans in poverty, the fascination with taxes I paid I find to be very small minded compared to the broad issues we face," he said. "But I did go back and look at my taxes and 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," said Romney today during a press conference on a tarmac in South Carolina, where the candidate came to attend a fundraiser.

During the interview with Muir in Jerusalem last month, Romney was asked whether he had ever paid a tax rate lower than the 13.9 percent effective rate he paid in 2010.

"I haven't calculated that," Romney responded at the time. "I'm happy to go back and look, but my view is I have paid all of the taxes required by law."

At the time, Romney's inability to answer the question led to criticism from Democrats who want Romney to publicly release tax returns. Romney has released his tax returns for 2010 and a preliminary filing for 2011.

One top Democrat, Sen. Harry Reid of Nevada , had accused Reid of not paying taxes in some years. Reid said he had gotten a tip from someone who had worked with Romney at Bain. But there is no evidence to suggest there was any validity to Reid's charge.

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With the comment in South Carolina on Thursday, Romney sought to put at least some of the questions to rest.

"So I've 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. But every year I've paid at least 13 percent and if you add in addition the amount that goes to charity, well the number gets well above 20 percent."

Democrats, predictably, said they won't believe Romney until he actually releases the tax returns.

"Since there is substantial reason to doubt his claims, we have a simple message for him: prove it,"said Obama campaign spokeswoman Lis Smith in a statement. "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. 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."

Reid spokesman Adam Jentleson, in a paper statement to ABC News, echoes the sentiment of the Obama campaign.

"Until Mitt Romney releases his tax returns, Americans will continue to wonder what he's hiding, he said."

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Read about David Muir's interview with Romney.

Watch it here: