US Democratic presidential candidate Barack Obama has accused former president Bill Clinton of making false statements about him.
Mr Obama took issue with Bill Clinton's criticism of his record
Mr Obama said Mr Clinton had taken his support for his wife, Hillary - Mr Obama's main rival for the nomination - to a level that was "troubling".
Mr Obama said his campaign team would have to directly confront the former president in future.
The criticism comes days before the South Carolina primary.
Mr Obama needs to win in South Carolina to re-invigorate his campaign after two recent defeats.
His comments came on ABC's network breakfast programme, Good Morning America.
"You know the former president, who I think all of us have a lot of regard for, has taken his advocacy on behalf of his wife to a level that I think is pretty troubling," Mr Obama said.
"He continues to make statements that are not supported by the facts - whether it's about my record of opposition to the war in Iraq or our approach to organising in Las Vegas.
"This has become a habit, and one of the things that we're going to have to do is to directly confront Bill Clinton when he's making statements that are not factually accurate."
Mr Clinton recently said that Mr Obama's claim that he consistently opposed the Iraq war from the start was "a fairy tale", and that Nevada union officials backing Mr Obama had suppressed the vote of Clinton supporters.
The Clinton campaign stood by the criticisms, saying "facts are facts".
"President Clinton is a huge asset to our campaign and will continue talking to the American people to press the case for Senator Clinton," spokesman Phil Singer said.
Mrs Clinton has won two of the three main primary contests so far - beating Mr Obama in Saturday's Democratic primary in Nevada.
Mr Obama won in Iowa, and polls suggest he is leading in South Carolina ahead of the Democratic primary there next Saturday.
The BBC's North America editor, Justin Webb, says the two candidates' mutual dislike appears to be intense and growing.