Chris Pincher was responsible for maintaining discipline among Conservative MPs before resigning last night.
He said he “embarrassed myself and other people” after drinking “way too much.”
The incident is said to have taken place at the Carlton Club, a private membership in Piccadilly in London, closely associated with the Tory party.
Mr Pincher resigned after allegedly assaulting two fellow guests on Wednesday night, The Sun said.
But since he was deemed to have done the right thing by admitting wrongdoing and stepping down, he is expected to sit as a Tory MP for the time being.
Labor said it showed the party was “entangled in sleaze and scandal” and wondered how Pincher could still take the Conservative whip.
In May, Tory MP for Tiverton and Honiton, Neil Parish, took his seat in the House of Commons in full after admitting to having watched pornography in the House of Commons.
That same month, Imran Ahmad Khan, a former Conservative Member of Parliament for Wakefield, convicted of sexually assaulting a 15-year-old boy in January 2008.
Parish’s resignation and Khan’s eviction led to two by-elections, both of which the Tories lost – prompting a minister to resign.
Deputy Labor leader Angela Rayner said the latest scandal “shows how far standards in public life have been compromised” under the Prime Minister’s oversight.
She added: ‘Boris Johnson has serious questions to answer about why Chris Pincher got this role in the first place and how he can remain a Conservative MP.
“The Conservative Party is so mired in sleaze and scandal that it is utterly unable to meet the challenges facing the British people.”
In his letter of resignation to the Prime Minister, Mr Pincher apologized for his behavior and said it had been “the honor of my life” to have served in government.
‘Last night I drank way too much. I have embarrassed myself and other people and that is the last thing I want to do and for that I apologize to you and those involved,” he said.
“I think it is appropriate in the circumstances that I resign as deputy head whip. I owe it to you and the people I upset to do this.
“I want to assure you that you will continue to have my full support from behind the benches. It has been the honor of my life to have served in Her Majesty’s Government.’
His departure in such dramatic circumstances is another blow to the Prime Minister who has been ravaged by allegations of misconduct over lockdown parties in Downing Street.
The Tamworth MP was appointed along with head whip Chris Heaton-Harris last February to bolster support for the prime minister amid growing unrest among Tory MPs over the ‘Partygate’ revelations.
It is the second time he has left the whip office, having resigned as a junior whip in November 2017.
This was in response to a complaint that he had made an unwanted pass on former Olympic rower and Conservative candidate Alex Story.
But after an investigation by the party, he was acquitted of violating the code of conduct.
After referring to both the police and the Conservative Party grievance procedure, he was brought back as a deputy head whip in January 2018 by Theresa May.
When Mr Johnson became Prime Minister in July 2019, he was transferred to the State Department as Secretary of State for Europe and America before returning to the whips office for a third time.
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