"It shows that bigotry still exists in some corners," said Romney, who spoke to reporters Wednesday after a campaign event. "I thought it was a most unfortunate comment to make."
On Monday, Sharpton said in a debate that "those of us who believe in God" will defeat Romney for the White House. He denied he was questioning the Mormon's own belief in God.
Rather, the New York Democrat said he was contrasting himself with Christopher Hitchens, the atheist author he was debating at the time.
"As for the one Mormon running for office, those who really believe in God will defeat him anyways, so don't worry about that; that's a temporary situation," Sharpton said during a debate with Hitchens at the New York Public Library.
Romney's campaign seized on the comments to criticize Sharpton, and the candidate complained about the remarks on Wednesday, calling them "terribly misguided."
Asked if he considered the civil rights leader a bigot, Romney demurred.
"I don't know Reverend Sharpton," he said. "I doubt he is personally such a thing, but the comment was a comment which could be described as a bigoted comment."
Romney added that he was willing to believe Sharpton didn't mean to be offensive.
"Perhaps he didn't mean it that way, but the way it came out was inappropriate and wrong," said Romney.
In a statement, Sharpton accused the Romney campaign of a "blatant effort to fabricate a controversy to help their lagging campaign" and argued that it was Hitchens who criticized Mormons.
"In no way did I attack Mormons or the Mormon Church when I responded that other believers, not atheists, would vote against Mr. Romney for purely political reasons," Sharpton said.
In an interview with The Associated Press on Tuesday, Sharpton denied questioning Romney's belief in God and suggested the Romney camp was trying to stir up a controversy because of their political differences.
"What I said was that we would defeat him, meaning as a Republican," Sharpton said. "A Mormon, by definition, believes in God. They don't believe in God the way I do, but by definition, they believe in God."
Romney, the former one-term governor of Massachusetts, said that as he campaigns, he hears little criticism about his religion.
"Overwhelmingly, the people I talk to believe that we elect a person to lead the nation not based on what church they go to, but based on their values and their vision," he said. "I receive very little comment of the nature coming from Reverend Sharpton."
The issue of Romney's religion is often compared to the scrutiny given to former President John Kennedy, whose Catholic faith was an issue in the 1960 campaign. Kennedy dealt with the matter by giving a high-profile speech in which he said his religion would not shape his policy choices.
Romney, the former governor of Massachusetts, hasn't addressed such questions so directly, but he has been clear that his religion wouldn't dictate his policies.
"I make it very clear that the doctrines of any one church are not the basis for electing any individual in this country — never have been and I doubt they ever will be," Romney said.