Michael Fallon resigns as Defence Secretary after saying past behaviour may have 'fallen below the high standards we require'

Sir Michael said behaviour acceptable a decade ago no longer is, as further incidents expected to emerge

Sir Michael Fallon has become the first major scalp claimed by the growing Westminster sexual harassment scandal, resigning from his cabinet job amid expected further allegations of inappropriate behaviour.

The ex-Defence Secretary who has been one of Theresa May’s most steadfast allies, admitted that in the past his actions fell “below the high standards” required of the armed forces he represented.

In an ominous sign for other ministers caught up in the sexual harassment scandal, he added: “We’ve all got to look back now at the past.”

Explaining his departure he said behaviour acceptable a decade ago no longer is, and the Prime Minister had made clear she wants staff protected and allegations of misconduct investigated, adding that from now on “it has to apply to all of us”.

The news will send a shockwave through Westminster which is reeling from fresh allegations on Wednesday – including that a male worker and female staffer had their crotches groped by different politicians and that another woman had her drink spiked with a ‘date rape’ drug in one of Parliament’s bars.

Other Tory ministers hit back against a ‘dirty dossier’ spreadsheet containing speculative allegations and being circulated on social media, with at least two consulting lawyers.

But an interview given by a crestfallen Sir Michael is likely to dominate the airwaves on Thursday.

The Tory veteran became snared in the sexual harassment scandal sweeping Westminster after it emerged he repeatedly put his hand on the knee of radio host Julia Hartley-Brewer during a party conference dinner in 2002.

The journalist threatened to punch him if he did it again, but said she had not regarded the incident as anything but “mildly amusing”.

Sir Michael had appeared to have ridden the storm out after Ms May said she would not launch a Cabinet Office investigation into the matter, as had happened with other ministers Mark Garnier and Damian Green.

But asked by BBC News after his resignation if more allegations are expected, Sir Michael said: “The culture has changed over the years.

“What might have been acceptable 15, 10 years ago, is clearly not acceptable now.

“Parliament now has to look at itself and the Prime Minister has made very clear that conduct needs to improve and we need to protect the staff at Westminster against any particular allegations of harassment.”

He explained, as he had done in his resignation letter, that he had in the past behaved in a way that was “below the standards that we require of the armed forces”, he had represented.

With other ministers facing allegations, Sir Michael said: “I think we’ve all got to look back now at the past, and there are always things you regret you will have done differently.”

He added during the interview that Ms May had told him staff at Westminster need to be better protected and that claims of harassment need to be properly investigated, adding: “The Prime Minister has now set that machinery in motion and clearly, that from now on has to apply to all of us.”

Sir Michael in a television studio earlier this year. He was seen as a 'safe pair of hands' to defend the Government in the media (EPA)

In his letter Sir Michael wrote: “A number of allegations have surfaced about MPs in recent days, including some about my previous conduct.

“Many of these have been false but I accept that 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.”

In her reply, Ms May said she appreciated “the characteristically serious manner” in which the minister considered his position, “and the particular example you wish to set to servicemen and women and others.”

Separately, a new allegation of sexual assault in Westminster emerged after a woman said a Conservative MP she worked for grabbed her by her crotch from behind.

She said she later told the Commons authorities about the incident, but was told there was “nothing they could do”.

Another former parliamentary intern revealed he was sexually assaulted by a former MP in 2012.

Under Secretary of State for International Trade Mark Garnier has admitted making his secretary sex toys and calling her 'sugar t*its' (PA)

James Greenhalgh, who did not know the MP, said: “His arm slipped down towards my buttocks, and he had a good feel round there and went a bit further in between my legs.”

He said when he tried to report the assault a couple of months later, he was told by the MP's party that he could not make a complaint anonymously so did not proceed.

In a separate incident, a former Conservative Party aide said her drink was spiked with a suspected ‘date rape’ drug in the Strangers’ Bar at the House of Commons. The bar is reserved for MPs and their guests.

On Tuesday evening Labour activist Bex Bailey said she had been raped as a 19-year-old at a Labour party even, but when she tried to report it two years later was told not to because it might “damage” her.

Labour has said it will appoint an independent investigator to look into the allegations made by Ms Bailey.

Some Conservatives were fighting back against claims made against them, in particular The Independent understands Mr Green has instructed libel lawyers Kingsley Napley after Times journalist Kate Maltby wrote that he made inappropriate advances to her.

Justice Minister Dominic Raab appeared in the ‘dirty dossier’ spreadsheet with Mr Green and said some of the accusations on it appeared little more than “gossip or unsubstantiated rumours”.

Dominic Raab during the EU referendum. He is consulting lawyers over claims made against him. (Getty)

In a post on his own website, he went on: “Under my own name, the entry reads: ‘Injunction for inappropriate behaviour with a woman’.

“And yet, I have never been served with any injunction for anything. Nor have I ever sought one. Equally, any insinuation that I have engaged in anything resembling sexual harassment, sexually abusive behaviour or lewd remarks with either parliamentary colleagues or staff (in any job I have done) is false and malicious. I have already taken legal advice.”

International Development Minister Rory Stewart is another Conservative whose name appeared on the list, in connection to a former aide, Sophie Bolsover.

But Mr Stewart tweeted: “This story is completely untrue + deeply hurtful. Neither of us have any idea how our names appeared on the list.”

Ms Bolsover said in a statement that she recognised the “seriousness” of some of the allegations being made more generally, but added: “I wish to emphasise that nothing of the kind implied by my name being included on this spreadsheet ever took place.”