John McCain, the US Republican presidential frontrunner, has denied having a romantic relationship with a Washington lobbyist after a report on the issue appeared in the New York Times newspaper.
McCain denied having an affair with Vicky Iseman, reported to have taken place eight years ago, and suggestions that he favoured her clients.
"Obviously I'm very disappointed in the article. It's not true," he said at a quickly organised news conference in Toledo, Ohio on Thursday.
The newspaper quoted aides as saying they had urged McCain and Iseman to stay away from each other before his failed presidential campaign in 2000.
"Something like this is always distracting and very disappointing and I hope we can, by doing what we're doing here, put to rest the whole situation," McCain said.
Past conduct
McCain also denied that he had ever improperly aided companies represented by Iseman as chairman of the senate commerce committee.
"At no time have I ever done anything that would betray the public trust," the senator said.
McCain is almost certain to win the Republican nomination for November's presidential election.
He and four other senators were accused two decades ago of trying to influence banking regulators on behalf of Charles Keating, a savings and loan financier later convicted of securities fraud.
The Senate Ethics Committee ultimately decided that McCain had used "poor judgment" but that his actions 'were not improper" and did not deserve punishment.
McCain has said that incident inspired him to attempt to change campaign finance laws in an attempt to reduce the influence of money in politics.
The Arizona senator is course to win the Republican nomination for president, but conservatives have voiced concerns over his record on immigration and tax issues.