Republican B.J. Lawson's campaign blamed a political consulting firm for duping it into believing Freeman had done the ad.
"This is terribly unfortunate and we apologize profusely to Morgan Freeman for what has happened," Lawson said. "This is obviously not something we ever would want to misrepresent."
Lawson's campaign had said earlier Monday that Freeman had done the narration for an advertisement posted online that attacked the Democratic incumbent, Rep. David Price. Freeman then issued a statement through his publicist that no one representing him had ever authorized the use of his name, voice or likeness in support of Lawson.
"These people are lying," Freeman said. "I have never recorded any campaign ads for B.J. Lawson, and I do not support his candidacy."
Later, Lawson's campaign said the political firm M.E.I. Political of Los Angeles was responsible. The company did not return a call seeking comment Monday.
The 30-second clip features a voice that sounds like Freeman's. It concludes, "It's time that you and I had a voice in Washington. Vote B.J. Lawson for Congress."
The ad has since been pulled from Lawson's website.
Lawson, who built his campaign with the support of conservative tea party activists, is running against Price in North Carolina's 4th Congressional District, which covers the Durham-Chapel Hill area and has a large bloc of black voters. Before Lawson's apology, Price said Monday that he thought Lawson's claim was deceptive and reckless.
"I just can't imagine that a responsible candidate or a responsible person would do this sort of thing," the lawmaker said.
Price was first elected in 1986, lost his seat in the Republican wave of 1994 and regained it two years later. His seat is widely considered safe in the Democratic-leaning district, but the veteran lawmaker has been airing ads targeting Lawson. Four of Price's Democratic colleagues in the North Carolina delegation are locked in costly re-election bids.
Freeman has supported Democratic candidates in the past, including Barack Obama in the 2008 presidential contest. He won an Oscar for his performance in "Million Dollar Baby" in 2004 and was nominated four other times. Freeman also recorded the voiceover introducing Katie Couric for the "CBS Evening News."