A Channel Four investigation has revealed that MP’s, especially Conservative MP’s, regularly got drunk and “flirted” or made passes at young male parliamentary workers during Commons drinking sessions.

One aide spoke of how he was approached to “go to the Gents” with an MP at an event for young political activists. “The MP suggested I go to the toilets with him at about 1am, but then at 3am I saw him going back to his hotel room with a guy who looked about 18.”.

Another said: “He invited the office to a gay bar, and came up to me and put his arm around my shoulder. Then one time he slid his hand right down my back, and I moved it away.”

The Channel Four programme showed that young men were far more likely to get harassed than women with two in five male workers claiming to have received unwanted sexual advances.

One woman described watching it happen: ”I watched men coming on to men, and men hiring men that they wanted to sleep with. I saw male MPs and researchers having relationships. When I was there, older men would explore their sexuality and be predatory to younger men.”

The investigation came after the closure of the trial of Nigel Evans. His trial had brought to light the sexual politics at play in Westminster and although he was cleared of all nine charges of rape and sexual assault, the former Commons Deputy Speaker admitted his involvement with a man 33 years his junior, who had done work experience in Westminster.

The court heard how Evans had been the “high watermark of over-friendly, inappropriate behaviour by a drunken man” but did not amount to any criminal offence.

Gay rights campaigner Ben Summerskill said: “Sexual harassment is part of the culture of Westminster. In the last decade I’ve heard of dozens of cases from men and women. People are vulnerable as they’re often political obsessives and have never worked anywhere else. For both sexes the MP can say that if they oblige them, it might help their career enormously.

“There’s no HR, no structure for people management or supervision.”

Last night, the Tories announced they were implementing a new code of conduct and a grievance procedure for MPs and their office staff.

It acts as a ‘basic statement of what should be best practice in the workplace for Conservative Members and their staff’, a spokesman said.

Commons Speaker John Bercow has also set up a helpline for staff of MPs from all parties.