Mr Oaten, who is married with two daughters, dramatically quit from his party's front bench team yesterday after he was confronted with details of an affair with a 23-year-old male prostitute.
The MP, who until last week was a candidate for the party leadership, quit as Home Affairs spokesman after he was confronted with details of sex with the prostitute by the News of the World. The former PR executive is reported to have had a "series of liaisons" with the rent boy over a six-month period which ended last February.
The newspaper confronted Mr Oaten yesterday morning with details of repeated encounters affair with the prostitute that included three-in-a-bed sex.
The revelation, which shocked and surprised his parliamentary colleagues, is the second scandal in less than a month to rock the Liberal Democrats.
The former leader Charles Kennedy made a public admission that he was an alcoholic and had been struggling with the condition for 18 months. Hewas forced to resign two weeks ago after a torrent of demands from his MPs who said he was not fit to carry on.
Mr Oaten, who had publicly supported Mr Kennedy and who used to be his parliamentary aide, issued a statement yesterday apologising "for errors of judgement in personal behaviour and for the embarrassment caused, firstly to my family but also to my friends, my constituents and my party".
An ambitious MP, Mr Oaten had made no secret of his desire to lead the Liberal Democrats. Last week, the MP, considered a rising party star, stood down as a leadership contender after it emerged he had the backing of only one MP.
Yesterday Mr Oaten asked for "space and personal privacy for me and my family".
Andrew Stunell, the party's chief whip, confirmed that Mr Oaten had stood down "with immediate effect" as Home Affairs spokesman. "He has apologised to his family. He has apologised to his constituents who he always served well," Mr Stunell said. "He and his family now need to have their personal privacy respected."
Last week, in a strange twist to a fraught leadership contest, he called in the police after an email between him and staff from Mr Kennedy's office was apparently stolen from his Commons office.
Mr Oaten says an email that indicated that staff from Mr Kennedy's office were helping him to launch his campaign had been stolen.
The former PR man won Winchester for the Liberal Democrats in May 1997 by two votes, but gained a massive majority in a by-election that November. He is a popular figure in the party and he and his wife, Belinda, who used to import clogs have two daughters.
One of the last initiatives by Mr Oaten as Home Affairs spokesman concerned prostitution.
Responding to the Government's strategy last week, the Liberal Democrat MP issued a statement called for "smart solutions" to tackle prostitution.
He said prostitutes, including rent boys, should be "subject to a code of conduct and regular contact with police and health workers.
"The object was not to 'tolerate' prostitution but to move it to a specified area where professionals can work with prostitutes to help them reach a point where they can choose other employment," he said.
The Statement: 'I would now ask for privacy'
Mr Oaten said tonight: "I have stood down as Home Affairs spokesman for the party. I would like to apologise for errors of judgement in personal behaviour and for the embarrassment caused firstly to my family but also to my friends, my constituents and my party.
"I will not be commenting further at this time and would now ask for some space and personal privacy for me and my family."Reuse content