Party whips gather information on misbehaviour by MPs but keep it secret to use it against them later, a former No 10 aide to Theresa May claimed today.

Katie Perrior hinted at the long-rumoured existence of an infamous 'black book' in the Tory whips office.

The former No 10 head of communications said the information was kept away from the Prime Minister.

Her intervention came on a day allegations of sexual harassment exploded into a major scandal at Westminster in the aftermath of allegations against Hollywood mogul Harvey Weinstein.

Ex-No 10 head of communications Katie Perrior (pictured on the BBC today) hinted at the long-rumoured existence of an infamous 'black book' in the Tory whips office

Ms Perrior said incriminating information was often 'kept away from the prime minister' but deployed by whips to enforce party discipline.

She told BBC Breakfast: 'The information is held by the whips, because they use it to make sure that MPs know that other people within the party know exactly what they've been up to.

'(They are told) that behaviour either is not acceptable, or it will be used against them – you will vote in a certain way or we will tell your wife exactly what you've been up to.'

The Westminster 'sex pest' row escalated today with warnings that MPs could face hundreds of allegations - and claims some could even be criminal.

The scale of the scandal appears to be widening after a 'dirty dossier' surfaced listing 36 sitting Conservative MPs.

Ms Perrior said the information was kept away from the Prime Minister (pictured in Downing Street today)

One was said to be 'handsy with women', another 'paid a woman to be quiet', while a former Tory minister was said to have propositioned his secretary by asking her to 'come and feel the length of my c***'.

Theresa May today vowed to act against MPs found to have harassed staff and refused to say she had confidence in a serving minister, Mark Garnier.

He faces a formal probe into claims he made his secretary Caroline Edmondson buy sex toys for him and called her 'sugar t*ts' in public. The International Trade minister denies sexual harassment and says the allegations are exaggerated.

Meanwhile, a Labour MP has warned that issues with sexual misconduct in Westminster go much wider - and cases could number in the hundreds.

Another MP said he was aware of four incidents, saying one 'passes the criminal threshold' and another is 'appalling'.