JOHN KERRY, the front-runner for the Democratic presidential nomination, last night denied rumours that he has had an extra-marital affair with an intern.

A day after the internet columnist Matt Drudge first posted the allegation on his website, triggering a furious dirty-tricks row, Mr Kerry told reporters that the report was untrue. “I just deny it categorically. It’s a rumour. It’s untrue. Period,” he said.

His statement followed an interview earlier yesterday, in which he failed to quash the rumour when questioned directly by one of America’s most popular talk radio hosts.

The host, Don Imus, broke the mainstream American media’s silence on the subject during a live interview with the Massachusetts senator.

“Is anything that’s going to come up, now, for example, there is this Drudge report about an intern . . . people are talking about it?” Mr Imus asked.

“Well, there is nothing to report. So there is nothing to talk about,” Mr Kerry replied. “I’m not worried about it. The answer is no.”

Meanwhile the rumours continued to swirl on the Drudge Report and other websites. A 24-year-old woman was named, and reported to be in hiding in Kenya with her fiancé. Her parents in small-town Pennsylvania said that Mr Kerry had invited their daughter to work on his Senate re-election campaign in 2001, but offered no evidence that there had been an affair.

Drudge claimed to have had more than 15 million hits on his website since breaking the story, but by yesterday afternoon only a handful of local television and radio stations across America had referred to the allegations.

Mr Kerry’s response left Democrats unsure whether to brace themselves for a scandal just as Mr Kerry had overtaken President Bush in the polls, or to watch the rumours melt into nothing.

Mr Kerry used his radio appearance to send a coded message to concerned Democrats.

Referring to his four successful Senate campaigns, he said: “I’ve been at this for a while and I’ve been through some tough races. I’ve been pretty well vetted and examined from one side to the other.”

In a message to the Republican opposition, the decorated Vietnam veteran said: “I think that they’re in for a surprise. I’m going to fight back. I’m a fighter, and I’m ready to fight back.”

Until Thursday, the result of the race for the Democratic presidential nomination had seemed all but assured. Mr Kerry’s perfectly timed recovery from last year’s slump to win 12 of the first 14 primaries had made him the favourite.

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