John McCain, struggling to consolidate his support in the conservative wing of the Republican party, was today forced to deny a report of an affair with a lobbyist for the telecommunications industry.

Flanked by his wife, Cindy, a subdued McCain told a press conference in Toledo, Ohio, there was no basis to a story in the New York Times of a relationship eight years ago with the lobbyist, Vicki Iseman. "It's not true," he said.

The newspaper had reported that aides to McCain had confronted Iseman in 1999 and told her to stay away from McCain because they were concerned that the tie to the lobbyist could hurt his political career.

This morning's appearance brought a decidedly muted response from McCain only hours after his aides railed against the story as "gutter politics" and a "smear campaign". Although McCain has a reputation on Capitol Hill as a man with an explosive temper, he spoke in a quiet voice and repeatedly emphasised his "disappointment" with the Times.

McCain's wife preserved the measured tone, stepping up only briefly to the microphone to say: "My children and I not only trust my husband but, more importantly, know that he would never do anything to disappoint our family and more importantly disappoint America."

As McCain himself acknowledged today, the allegations appear at a delicate time. After hauling his campaign back from the brink of collapse last summer, he is virtually assured of winning the Republican nomination against Mike Huckabee. However, despite an insurmountable lead in the delegate race, McCain has yet to win the trust of the conservative wing of his party.

In addition to allegations of an affair, the suggestion of overly close links to lobbyists have the potential to damage McCain. The Vietnam war hero has built his candidacy around his reputation as a crusader against Washington's monied interests, as symbolised by his campaign bus, which he calls the Straight Talk Express.

In 2000, McCain put his opposition to corporate interests at the centre of his failed campaign for the Republican nomination against George Bush.

The Times had been pursuing the story for months and by the time it published today, other news organisations, including the New Republic, had their own versions of the relationship between McCain and Iseman.

The newspaper said McCain had complained about its investigation during a telephone call with its executive editor, Bill Keller, in which the senator had also denied an affair with Iseman.

At the time of the alleged affair, McCain was chairman of the Senate's powerful commerce committee. Iseman was working on behalf of a small media chain which was seeking support from Congress for its purchase of a Pittsburgh television station.

McCain wrote two letters urging the Federal Communications Commission, the regulatory authority, to issue a decision. But he insisted today he did not advocate on behalf of Iseman's client, but merely pressed the FCC to speed up its process.

The newspaper said Iseman was a frequent visitor to McCain's Senate office and that he had flown with her on a corporate jet belonging to her client, Paxson communications.

It quoted a former strategist for McCain, John Weaver, as saying in an email that he had arranged a meeting between an aide and Iseman at Washington's Union Station to ask her to stay away from the campaign.

"Our political messaging during that time period centered around taking on the special interests and placing the nation's interests before either personal or special interest," the newspaper quoted Weaver saying.

"Ms. Iseman's involvement in the campaign, it was felt by us, could undermine that effort."

McCain denied any knowledge of such concern among his aides today, or of any such meeting with Iseman. He insisted that he was not unduly influenced by any of his contacts with lobbyists in Washington.

"I have many friends who represent various interests ranging from the firemen to politics to senior citizens," he said. "The question is whether they have unwarranted access or interest and certainly no one ever has."|

The newspaper also revived memories of a 1989 scandal involving the collapse of the Lincoln Savings and Loan Association which cost taxpayers $3.4 billion. Five senators, including McCain, were reprimanded for acting on behalf of the bank's chief, Charles Keating, who was jailed in the affair.

However, some commentators suggested today that the attack might actually bolster McCain's credentials among conservatives, who view the Times with suspicion as a liberal newspaper.

The allegations in the Times also provide potential ammunition to Barack Obama, who is favoured to be McCain's opponent next November, and who has based his campaign message on the need for change in Washington.

Later, the McCain campaign launched a fundraising appeal based on the New York Times' story.

"The New York Times ... has shown once again that it cannot exercise good journalistic judgment when it comes to dealing with a conservative Republican," McCain campaign manager Rick Davis wrote in an e-mail to supporters. "We need your help to counteract the liberal establishment and fight back against The New York Times by making an immediate contribution today.

"We think the story speaks for itself," Times executive editor Bill Keller said in a written statement. "On the timing, our policy is we publish stories when they are ready."