Labour MP Chris Bryant has claimed a Daily Mail journalist told him in 2003 that people were “taking bets” on when he would kill himself.
The Rhondda MP was in the headlines at the time after he apologised for emailing a picture of himself in his underpants via a gay website.
He said there was “no justice” for MPs who faced “trial by front page”.
The Daily Mail said his claim was a “scurrilous smear” and he should withdraw it immediately.
Mr Bryant was taking part in a debate on new grievance procedures to deal with complaints of sexual harassment.
The former minister said he was concerned about the lack of gay representatives on a cross-party working group, including staff representatives, on new procedures and that it was too dominated by MPs.
But he added: “My biggest anxiety of all is that you have to have justice for both sides. If you just have trial by newspapers and trial by front page that is not justice.
“That is not justice for young people, for the people who feel they have been abused and want to make allegations.
“Nor is it justice for those at the other end. I remember in 2003 a journalist from the Mail on Sunday coming up to me in the Strangers’ Bar and saying ‘we are all taking bets on when you will commit suicide. I hope it’ll be before Christmas’.”
Mr Bryant later said on Twitter that he had “misspoke” and it was a journalist from the Daily Mail.
A spokesman for the Daily Mail said: “This is not the first time Mr Bryant – who is a prominent supporter of [campaign group for greater press accountability] Hacked Off and has a long history of hostility to the Mail – has peddled this scurrilous smear.
“He attempted to include it in his evidence to the Leveson Inquiry [into press ethics], but not only did the journalist concerned categorically deny making the remark, he denied ever having met Mr Bryant.
“The identity of the journalist, who left the Mail many years ago, was redacted from Mr Bryant’s evidence by the inquiry.
“It is utterly disgraceful that Mr Bryant should use parliamentary privilege to repeat an allegation that was rejected by the Leveson Inquiry. He should withdraw it immediately.”
Commons leader Andrea Leadsom said she was “sorry to hear” about Mr Bryant’s alleged experience.
“That is really, truly appalling and I think we all recognise there is a challenge here with living in the public eye and often allegations which are either spurious, or indeed malicious, or designed to hurt can be made at individuals and that’s not right.
“And much as as we are seeking here to provide justice to those who work here and at all levels, whether they are young and extremely inexperienced or whether they have been here a long time, whether they are LGBT plus or straight, or whatever their race or ethnic background, we are seeking to ensure that there is justice for all.”
Mrs Leadsom said proposals for a new system to provide advice and action on bullying and harassment in Parliament would be published before MPs break for Christmas.
Several MPs stressed the need for a specific sexual harassment policy to be established.
Labour MP Jess Phillips welcomed Mrs Leadsom’s statement but said: “I notice it doesn’t say the word sexual harassment in it once.”
She backed calls for a “specialist sexual violence service” to give advice to the working group and for people working in Parliament afterwards.
Mrs Leadsom said an independent expert in sexual harassment will advise the working party.
She also confirmed that the new procedure would be open to all pass holders on the Parliamentary estate, including contractors and journalists.
And she said the working group would be considering the appropriate sanctions against MPs who had been found to be guilty of harassment, including recall elections so that MPs could be ejected from Parliament.
At the moment, MPs who have been kicked out of their parties can continue to sit on the Commons benches as independents and carry out constituency duties, including meeting the public at surgeries.