Boris Johnson’s deputy chief whip has resigned over an allegation of groping, Sky News understands.
Chris Pincher, 52, said he had drunk “far too much” and had “embarrassed myself and other people” on a night out.
“I apologize to you and to those concerned,” he added in a letter to the prime minister.
Mr Pincher “groped two men in front of others” at the Carlton Club in the St James’s area of central London, a government source told Sky News.
One of those groped is an MP, and the second one may be a member of parliament too, the source added.
Labour’s deputy leader, Angela Rayner, said Mr Johnson had “serious questions to answer” about why Mr Pincher had been “given this role (as deputy chief whip) in the first place and how he can remain a Conservative MP”.
His departure comes less than a week after former Tory chairman Oliver Dowden stood down over two by-election defeats.
It is the second time Mr Pincher has quit the whips office.
In November 2017, Downing Street said he had “voluntarily referred himself both to the party’s complaints procedure and the police”.
The Mail on Sunday reported that Mr Pincher had been accused of making an unwanted pass at Conservative activist and former British rower Alex Story.
Mr Pincher told the newspaper: “If Mr Story has ever felt offended by anything I said then I can only apologize to him.”
Theresa May reappointed him to the whips office the following year.
In his letter to Boris Johnson, the Conservative MP for Tamworth wrote: “Last night I drank far too much.
“I’ve embarrassed myself and other people which is the last thing I want to do and for that I apologize to you and to those concerned.
“I think the right thing to do in the circumstances is for me to resign as deputy chief whip.
“I owe it to you and the people I’ve caused upset to, to do this.”
Mr Pincher added: “I want to assure you that you will continue to have my full support from the back benches, and I wish you all the best as you deal with aftershocks of COVID and the challenges of international inflation.
“It has been the honor of my life to have served in Her Majesty’s Government.”
Ms Rayner said the resignation showed “how far standards in public life have been degraded on Boris Johnson’s watch.”
She added: “The Conservative Party is so looked at in sleaze and scandal that it is totally unable to tackle the challenges facing the British people.”
Mr Johnson has been fined by the Metropolitan Police for breaking lockdown rules.
In May, Neil Parish resigned as a Conservative MP after admitting watching pornography in the House of Commons.
Chris Pincher has been an MP since the 2010 general election, when the Conservatives formed a coalition with the Liberal Democrats.
Before his latest spell in the whips office he was minister of state for Europe and the Americas, and minister of state for housing.
He also writes a column on alcoholic drinks for The Critic magazine. A recent one was headlined: “Fall into the gin trap.”
The Tories are not the only party experiencing sleaze allegations at present.
Earlier this month, it emerged that SNP MP Patrick Grady was facing suspension from the House of Commons after an allegation of sexual misconduct was upheld following a parliamentary investigation.
An independent expert panel recommended that Mr Grady be suspended from the House for two days for making an “unwanted sexual advance” to a member of party staff at a social work event at a pub in 2016.
Mr Grady was also ordered to make a public apology in the chamber and to say sorry privately to the person who complained.
The SNP’s leader in Westminster, Ian Blackford, has faced calls to step down in connection with the same matter.