Westminster engulfed in growing scandal as nearly 40 MPs, including Cabinet and former Cabinet ministers, are accused of inappropriate behaviour including sexual harassment.

Dossier put together by Westminster researchers accuses MPs of sexual harassment, unwanted advances and extramarital sex with parliamentary staff.

Theresa May and government whips were allegedly aware of allegations made against Conservative MPs.

Four Labour MPs are also accused and the party fears more will emerge.

LONDON — Theresa May is under pressure to explain exactly when she knew about the scale of the growing sexual harassment scandal in Parliament after dozens of Tory MPs were engulfed in allegations of unwanted sexual advances and behaving inappropriately towards members of staff.

A group of Westminster researchers have put together a list of nearly 40 Conservative MPs, including several members of May's Cabinet, who have had allegations made against them over the last five years, according to The Times.

The prime minister has been aware of the allegations, The Times claims, because government whips have been giving her weekly briefings on accusations made against her MPs by Westminster employees. May's spokesperson will this morning face questions from journalists about exactly what the prime minister knew and when.

The scandal is expected to spread over the coming days with at least four Labour MPs also accused of harassing young women who work in Westminster, including two who have at some point served in leader Jeremy Corbyn's shadow Cabinet.

May has written to the House of Commons Speaker, John Bercow, urging him to establish a mediation service for Westminster staff wanting to report the inappropriate behaviour of MPs, the Guardian reports.

The Independent Parliamentary Standards Authority has recommended that a grievance procedure is incorporated in contracts of Westminster employees, providing them with a means of raising concerns and complaints.

However, MPs are technically self-employed, meaning they are not legally obliged to provide this outlet to their employees.

"It does not have the required teeth as contractually an MP does not have to follow the procedure. I do not believe this situation can be tolerated any longer," the prime minister said in a letter to Bercow.