Fred Thompson's campaign lashed out at Mitt Romney Wednesday after one of Romney's key supporters suggested Thompson's recent endorsement by the anti-abortion National Right to Life Committee was traded for cash.

In an article in The Washington Times on Wednesday, Paul Weyrich — the socially conservative co-founder of the Moral Majority who is backing Romney for president — is quoted saying that Thompson's endorsement from NRLC "makes no sense" and speculated that it had been motivated by a pecuniary relationship.

"I think in all probability the Thompson people were engaged with the National Right to Life people in financial dealing," Weyrich told the newspaper.

Click here to read the article in The Washington Times.

Neither Thompson's camp nor the anti-abortion group itself took the charge sitting down.

"It is unseemly for the Romney campaign and its supporters to suggest that NLRC-PAC's coveted endorsement is based on a bribe. Second, this unfounded accusation is as outrageous as it is ironic, given the Romney campaign's long history of spreading money around to anyone who will take it," said Thompson spokesman Todd Harris

"The Romney campaign was clearly hoping for this endorsement and are now clearly upset. But being denied an endorsement is no excuse to impugn the integrity of the very organization they were just days ago trying to woo," Harris continued.

NRLC Executive Director David O'Steen told FOXNews.com that Weyrich's claim was "totally, totally false."

“There's no financial arrangement with the Thompson campaign. We never asked the Thompson campaign for any financial consideration. They have not given us any financial consideration. We’re not going to ask them for a contribution," he said. "There is absolutely no basis in fact for that."

O'Steen said the organization is not even permitted to take contributions from a political party or committee anymore, even though that used to be common practice. Weyrich cited this practice in explaining his remarks.

Skepticism about Thompson's endorsement from the nation's largest anti-abortion organization came after Thompson said recently on NBC's "Meet the Press" that he would not support a constitutional ban on abortion, and that the legality of abortion should be left to the states.

He later said his record is still "100 percent pro-life."

A spokesman for Romney had no comment on Thompson's remarks, or on Weyrich's claim. Weyrich told FOXNews.com that he had not spoken to Romney before making the comments, but that he stands by what he said.

"I can't understand any other reason for that endorsement in light of what Thompson has said" on the matter, Weyrich said.

FOXNews.com's Judson Berger and FOX News' Shushannah Walshe contributed to this report.