GREER, S.C. — Republican presidential candidate Mitt Romney said Thursday that he has never paid less than 13 per cent of his income in taxes the past decade.

But he declined anew to release the records to prove it.

“I did go back and look at my taxes and over the past 10 years I never paid less than 13 per cent. I think the most recent year is 13.6 or something like that. So I paid taxes every single year,” Romney told reporters after landing in South Carolina for a fundraiser.

Romney has released his 2010 tax return and has pledged to release his 2011 return before the Nov. 6 election, but has refused to release earlier returns.

Democratic Senate Majority Leader Harry Reid, citing an anonymous source, has charged Romney didn’t want to release any more of his returns because the Republican candidate had paid no taxes in some years.

“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,” Romney said.

Obama campaign Lis Smith responded by telling Romney to “prove it.”

“He has forfeited the right to have us take him just at his word,” Smith said.

White House spokesman Jay Carney said Democratic President Barack Obama believes “the tradition for presidential candidates to put forward multiple years of their tax returns is a useful and valuable one. Not always comfortable.”

Romney commented as his campaign worked to stay on the offensive in the increasingly heated debate over Medicare, the health-care program relied upon by millions of seniors.

“Which of these two do you think is better?” Romney asked as he stood next to a whiteboard comparing his Medicare plan with Obama’s.

“The president was talking about Medicare yesterday. I’m excited about this,” Romney’s running mate, Paul Ryan, added during an appearance in Ohio. “This is a debate we want to have, this is a debate we need to have and this is a debate we’re going to win.”

The Wisconsin congressman’s addition to the Republican ticket drew immediate scrutiny to a budget proposal he drafted to transform Medicare into a voucher-like system for future retirees.

In turn, Romney and Ryan called attention to President Barack Obama’s health care law, which is funded in part by future savings from Medicare, and accused him of “raiding” the program of billions of dollars.

“What he probably did not mention yesterday is that when he passed his signature health care achievement, Obamacare, he raided $716 billion from Medicare to pay for Obamacare,” Ryan, chairman of the House Budget Committee, said. “This will lead to fewer services for seniors.”

What Ryan doesn’t say is that his proposal includes the same savings, supposed to be realized through lower payments to hospitals and doctors, and by making the program more efficient.