John Prescott fell victim to internet "bloggers" yesterday as the spotlight returned to his private life.
The Deputy Prime Minister refused five times to deny he had had more than one marital affair, in a dramatic exchange with Radio 4 interviewer John Humphrys.
The questions were prompted by reports on various web sites of unconfirmed stories the newspapers dare not print.
Web sites run by amateur journalists are already recognised as a powerful feature of American politics, and the most well-known, the Drudge Report, is frequently mentioned on The West Wing, a drama about life in the White House.
But their British equivalents have never before received much attention at home.
Newspapers have been chasing rumours about Mr Prescott's private life since it emerged he had an affair with his secretary, Tracey Temple.
But they have not been able to obtain evidence to stand up their stories.
Instead, rumours have been spread on internet "blogs", which can be put together by anybody with a computer and a phone line.
The operators may believe they are less likely to be sued for libel than a newspaper. But yesterday, Mr Prescott hinted they will face legal action.
He was also quizzed about the controversial visit he made to the Colorado ranch of Philip Anschutz, the tycoon who wanted to put a super-casino on the site of the Millennium Dome.
The Parliamentary anti-sleaze watchdog, Sir Philip Mawer, announced he will be holding a full inquiry into the allegation that Mr Prescott breached the rules by failing to declare hospitality from the US billionaire.
And at the same time, the chairman of the Committee on Standards in Public Life, Sir Alistair Graham, said Tony Blair would face serious criticism if he failed to deal with the controversy.
Downing Street continued to offer Mr Prescott full support but refused to defend him in detail.
Mr Prescott appeared on Radio 4's Today programme to try to quash rumours he was on the brink of quitting.
But he found himself facing a grilling from Mr Humphrys, who focused on the internet rumours.
Mr Humphrys asked him: "There are now reports, and they're circulating on the internet, as you know, that you have had other affairs. Is that true?"
Throughout the course of the interview the presenter put the question directly to Mr Prescott four more times, but did not receive a direct answer. At one point he warned: "You're talking about a lot of people here who have in fact denied these stories, names have been mentioned, some of them are in the process of perhaps suing about it."
And he insisted he would not quit.
"I will get on with doing my job and I am not leaving it, I am getting on with it," he said.
The Deputy Prime Minister was later defended by Lord Rooker, the former MP for Perry Barr in Birmingham and now an Environment Minister. Lord Rooker said: "The facts are the last thing some people in the media want to have out in the open."
Tories demanded the Prime Minister order Sir John Bourn, his adviser in Ministerial conflicts of interest, to begin an inquiry.
Hugo Swire, shadow Culture Secretary, said: "It is essential to the integrity of government, and the Ministerial code itself, that Sir John is allowed to examine all the facts, and I would urge Sir Gus O'Donnell to take action over my request as a matter of urgency."