An all-male hierarchy has created a culture in Parliament in which the sexual harassment of junior members of staff has been allowed to thrive, Harriet Harman, Labour's deputy leader, claimed Saturday.
Her comments came amid growing concern that sleaze was engulfing the Palace of Westminster, dubbed the "Palace of Sexminster" in some quarters.
On Saturday, Parliament's expenses watchdog announced it was to investigate claims that taxpayers indirectly funded a hotel suite used for a gay sex party during a Conservative Party conference.
The hotel room, which cost £2500 a night, was reportedly booked by the Policy Research Unit (PRU), an organisation that provides parliamentary research for Conservative MPs, which is overseen by senior figures in the party.
In further claims that sexual harassment was rife, William Hague's former female spin doctor during the time he was party leader claimed that she had been sexually assaulted "many times" by male MPs.
Amanda Platell said: "The truth is that there is an entrenched subculture of louche, predatory and deeply unpleasant behaviour - the sad fact is that too many MPs live in an amoral vacuum."
Miss Platell said one married shadow cabinet minister had "regularly grabbed my backside"; that another married MP, after a long lunch, "had tried to kiss me roughly" and another politician had knocked on her hotel room door at 1am at a residential conference and "made a lascivious lunge at me".
Miss Platell's claims were echoed by Ms Harman, deputy leader and shadow culture secretary, who said on Saturday that a late-hours, macho culture had stoked the problem.
Ms Harman said: "Certainly when I first arrived [in Parliament] if you had very, very long hours, people working beyond 10pm, if you have people away from home and you have a male hierarchy, that is a recipe for a culture in which sexual harassment can prevail.
"And therefore you have to have very strong procedures and send down the message that this is not acceptable, that you should be encouraged to complain and your complaint will be dealt with."
Ms Harman said that Labour was revisiting its codes of conduct in the light of questions over the behaviour of MPs towards younger members of staff.
She told the BBC's Today programme: "When it comes to sexual harassment, we certainly have been looking again at our codes of conduct which we've had for some time in the party, which sets out specifically what behaviour is not acceptable for an employer towards their employee in terms of sexual harassment and what the procedures are to deal with it."
Last week, a Channel 4 News investigation claimed there was a prevailing climate of sexual harassment in Parliament after interviewing 70 people from "all political parties and sexual orientations".
It said that young men were more likely to be sexually harassed than women, with 40 per cent of the men interviewed saying they had received unwanted sexual advances.
A third of those interviewed said they had personally experienced sexual harassment, while almost a quarter said they had witnessed someone else being sexually harassed, or that a friend had confided in them about being harassed.
The investigation into the spending of taxpayers' money on a suite of hotel rooms, where a gay sex party was allegedly held during the Conservative Party conference in Manchester in 2011, was announced by the Independent Parliamentary Standards Authority (Ipsa).
A spokesman said the investigation would centre on whether the room was used for legitimate parliamentary research purposes. MPs can claim expenses for paying for researchers, but the money cannot be used for "party political activity".
An Ipsa spokesman said: "MPs are not allowed to claim costs which go to party political activities. If there are suggestions that that may have happened, we would want to look into it."
It is claimed that the suite was booked by a senior aide at a cost of £2500 for one night at the Light ApartHotel in Manchester. It is claimed the aide had indirect access to taxpayers' money through the PRU, which is funded mostly by MPs' expenses.
It is also alleged that the gay sex party was organised through Grindr, a computer app that enables users to make contact with fellow gay men in the vicinity.
It is understood that concerns were raised with senior Conservative officials that the party was being "advertised" on Grindr.
Oliver Heald, the Conservative MP who at the time was the chairman of the PRU, confirmed that members of the research team did attend party conferences. But he insisted the attendance was audited by PRU's treasurer and that he was unaware that such expenditure might breach rules set down by Ipsa.
Henry Bellingham, the current PRU chairman, said the majority of PRU's funding came through the parliamentary expenses scheme. He said no one from PRU - to his knowledge - had attended the Conservative Party conference since he took over as chairman in 2012.