THE sexual harassment scandal gripping Westminster has claimed its first Cabinet victim with the resignation of Sir Michael Fallon, the Defence Secretary.

The 65-year-old Scot said in a letter of resignation to Theresa May last night that a number of allegations had been made in recent days, “including some about my previous conduct”.

It comes after the Tory veteran apologised over an incident 15 years ago in which he made unwanted advances to the journalist Julia Hartley-Brewer, repeatedly placing his hand on her knee.

Sir Michael added: “In the past, I have fallen below the high standards that we require of the armed forces that I have the honour to represent. I have reflected on my position and I am therefore resigning as Defence Secretary.”

One colleague said: “Julia’s a good friend of Michael’s. He overstepped the mark when he put his hand on her knee. She made clear it was unwelcome and he rightly apologised 15 years ago.”

Ms Hartley-Brewer, now a radio host, insisted that, “no-one was remotely upset or distressed” by the incident.

She reacted with shock to Sir Michael’s resignation, tweeting: “Bloody hell. Sir Michael Fallon has just resigned as Defence Secretary.” She added that “I doubt my knee was the reason” for his resignation.

Defence sources suggested the former Cabinet minister had told the Prime Minister he could not “guarantee there wouldn’t be more incidents like Julia Hartley-Brewer”.

Earlier this week, his name appeared on the unverified list of sexual misconduct allegations, which has been circulating in Westminster.

In her response, the Prime Minister told her colleague: “I appreciate the characteristically serious manner in which you have considered your position and the particular example you wish to set to servicemen and women and others.”

She praised his long and impressive ministerial career – Sir Michael also served in various ministerial roles in the Thatcher, Major and Cameron governments – and work in championing the armed forces and work in helping the UK combat Islamic State.

Liberal Democrat Chief Whip and Orkney and Shetland MP Alistair Carmichael said: “Theresa May’s Cabinet is falling apart like a cheap piece of flat-pack furniture.

“As we face the biggest negotiations in the modern history of this country her ministers can’t even agree to sit around the same table. Her Cabinet is more divided than the 27 EU nations it is meant to be negotiating with.

“Theresa May lacks the authority to lead this country and her government is in meltdown. She has to change or leave. There are no other options.”

Politically, Sir Michael’s resignation is a major blow to the Prime Minister, already under intense political pressure over Brexit. It leaves her facing a reshuffle and deprives her of one of her most experienced Cabinet ministers.

Early speculation about Sir Michael’s replacement included a possible Cabinet move for fellow Scot Michael Gove, a promotion for Brandon Lewis, the Immigration Minister, or Ben Wallace, the Security Minister. A former Sandhurst soldier, he began his political career as a list MSP in the first Scottish Parliament in 1999. Downing Street fears that Sir Michael’s resignation will not be the last and that his decision could put pressure on others.

The Scot was not under investigation about the 2002 incident but two of his former ministerial colleagues are the subject of probes.

Cabinet Secretary Sir Jeremy Heywood is looking into claims made against Mrs May’s deputy Damian Green.

The Cabinet Office investigation was launched after activist Kate Maltby, who is three decades younger than the First Secretary of State, told The Times that Mr Green “fleetingly” touched her knee during a meeting in a Waterloo pub in 2015 and a year later sent her a “suggestive” text message after she was pictured wearing a corset in the newspaper.

He has denied there making any kind of sexual advance to Ms Maltby, or putting his hand on her knee.

The department is separately probing whether international trade minister Mark Garnier breached the ministerial code after he reportedly admitted asking his secretary to buy sex toys and calling her “sugar tits”.

The shock Cabinet resignation came just hours after Mrs May had invited Westminster’s party leaders to crisis talks on Monday to discuss plans for tackling sexual abuse and harassment.

She said MPs from all parties were “deeply concerned” about allegations that have emerged in recent days as she invited political counterparts to talks on setting up a new “transparent, independent” grievance procedure.

“We have a duty to ensure that everyone coming here to contribute to public life is treated with respect,” she told MPs at Prime Minister’s Questions.

Meanwhile further allegations of abuse in the corridors of power continued to surface.

*A woman said a Tory MP she worked for sexually assaulted her in a Commons Office but was told by the Westminster authorities there was “nothing they could do”.

*A former Tory aide went to the police, claiming her drink had been “spiked” at a Commons bar with a suspected date rape drug. A police officer told her it was “not the first time” such an allegation had been made.

*James Greenhalgh, a former Commons intern, claimed in 2012 he was groped by a now ex-MP, saying: “I felt violated. It was awful.”

These latest claims follow that of prominent Labour activist Bex Bailey, who was discouraged by a party official from reporting an alleged rape at a Labour event in 2011 because they claimed it could harm her career.

In a separate development, two ministers named on an unverified list of sexual misconduct allegations in Westminster denied any wrongdoing.

Justice minister Dominic Raab said he had taken legal advice after his name appeared on the document next to a claim he was subject to an injunction for “inappropriate behaviour with a woman”.

Overseas aid minister Rory Stewart said claims about his behaviour towards a female member of staff were “completely untrue”, something the researcher publicly backed up.