Deputy Prime Minister John Prescott has admitted he had an affair with one of his secretaries.
The affair is reported to have started at an office party
The MP for Hull East said he regretted the relationship with Tracey Temple, 43, which had ended "some time ago".
"I have discussed this fully with my wife Pauline who is devastated. I would be grateful if [we] can get on with our lives together," a statement said.
Tony Blair's spokesman said Mr Prescott had strong support and was a "real benefit" to the country and government.
The spokesman added that Mr Prescott, 67, played "an absolutely vital role".
Downing Street had earlier said it was a "private matter", a message repeated by Home Secretary Charles Clarke when he appeared on BBC Radio 4's Today programme.
Mr Prescott and Ms Temple started meeting in secret at his Whitehall flat after a two-year relationship began at an office party in 2002, the Daily Mirror reported.
The pair began working together when Ms Temple was appointed as Mr Prescott's assistant private secretary, responsible for organising his diary, said the paper.
She had reportedly previously worked as a personal diary secretary for former Northern Ireland Secretary Mo Mowlam, who died of cancer last year.
The PM's spokesman said Mr Prescott had not offered to resign, nor had he abused his position by having an affair with a civil servant.
Ms Temple's boyfriend, lorry driver Barrie Williams, 46, told the Daily Mirror: "I just can't believe that my darling Tracey has been sleeping with John Prescott behind my back.
"How dare he split up my relationship with the woman I'd planned to marry!"
Mr Williams, of Bordon, Hants, said Ms Temple asked him to marry her just two days after she began a relationship with Mr Prescott.
"I'm just glad we hadn't got round to tying the knot," he said.
The Daily Mirror's associate editor, Kevin Maguire, said the affair had "some political ramifications, although... it would be wrong to overstate them".
"It's embarrassing for the government because of its current problems with cabinet ministers of one sort or another. It's very embarrassing for John Prescott publicly," Mr Maguire said.
The pair had a two-year relationship
"It will undermine his 'honest John' image to some extent and perhaps even make more difficult that broker role he's playing between Gordon Brown and Tony Blair."
Uniformed police were stationed outside the Prescott house in Hull on Wednesday and the gates were shut, with no sign of John or Pauline Prescott.
They have been married for more than 44 years and have two children.
The Daily Mirror's assertion that the affair was common knowledge in Mr Prescott's department was dismissed by local government minister Phil Woolas.
"I think it is a private matter for the Deputy Prime Minister," he said.
"I have worked for him for many years and I have every confidence in his ability, not just as a public spokesperson for the government but as the chair of Cabinet committees and as deputy to the Prime Minister and standing in for him, and in leading his department."