A Labour MP has quit his position on the Commons Women and Equalities Committee over a series of offensive online comments about celebrities made before he was elected.
Jared O'Mara joked about having an orgy with members of Girls Aloud, claimed Michelle McManus only won Pop Idol "because she was fat" and suggested it would be funny if jazz star Jamie Cullum was "sodomised with his own piano".
After the comments appeared on the Guido Fawkes website, Mr O'Mara issued a statement apologising for the remarks which he said were offensive and unacceptable.
His office said that he had also stood down from his position on the Women and Equalities Committee, informing MPs of his decision at the weekly meeting of the Parliamentary Labour Party.
"He has decided to stand down. He has made that decision," a spokesman for the MP said.
Sheffield Hallam MP Mr O'Mara, who ousted former deputy prime minister Nick Clegg in the June election, said: "I am deeply ashamed of the comments I made online, which have emerged today.
"I was wrong to make them, I understand why they are offensive and sincerely apologise for my use of such unacceptable language.
"I made the comments as a young man, at a particularly difficult time in my life, but that is no excuse.
"Misogyny is a deep problem in our society.
"Since making those comments 15 years ago, I have learned about inequalities of power and how violent language perpetuates them.
"I continue to strive to be a better man and work where I can to confront misogyny, which is why I'm so proud to sit on the Women and Equalities Select Committee.
"I will continue to engage with, and crucially learn from, feminist and other equalities groups so as an MP I can do whatever I can to tackle misogyny."
In a comment posted on the Drowned in Sound music website in 2004, Mr O'Mara said: "Girls Aloud - I advise you to sack Sarah and the remaining four members (Nicola, Cheryl, Nadine and Kimberley) come have an orgy with me."
In March 2004 on the same forum, he suggested Pop Idol's 2003 victor McManus "only won because she was fat".
Mr O'Mara, who has cerebral palsy, added: "Being a disabled person, I would hate to win something because people thought I was 'brave' or felt sorry for me, rather than for my superior ability/talent."
In the same post, he said of Cullum: "It would be no great loss to the music world if he was sodomised with his own piano and subsequently died of a sore arse.
"In fact, it would be quite funny."
Liberal Democrat peer and former leader of Sheffield Council Lord Scriven said: "It seems like a nasty pattern of sexist language and misogyny is developing from the Labour MP for Sheffield Hallam."