Chris Pincher quit on Thursday after an incident in which he "drank too much" and "embarrassed" himself. Political Correspondent Daniel Hewitt has the latest.
Boris Johnson was unaware of sexual misconduct allegations facing his former deputy chief whip before appointing him to the role, Number 10 has claimed.
Chris Pincher resigned as one of the government's top discipline enforcers last night after being accused of "groping" two men - but he was the subject of two other similar allegations just three years before getting the job.
He was accused of making an unwanted pass towards former Olympic rower and Conservative activist Alex Story in 2017, over an incident which allegedly took place in 2001.
The MP referred himself to the Conservative Party's disciplinary procedure and police over the reported incident however officers opted to take no further action.
But a Number 10 spokesman told reporters on Friday: "I'm not aware of the prime minister being aware [of the allegations] before any appointment.
"You'll be aware of the process that ministerial appointments go through and in the absence of any formal complaints, it was not appropriate to stop an appointment on the basis of unsubstantiated allegations."
On Thursday evening, Mr Pincher told the PM he was stepping down as deputy chief whip because he had "drank too much" and "embarrassed" himself.
According to The Sun, he was allegedly seen acting in a sexually inappropriate way toward two men on Wednesday night at the Carlton Club - a Tory Party private members' club in central London.
ITV News understands two Tory MPs complained to whips about Mr Pincher.
The PM is now under pressure to suspend him from the Tory Party, while opposition parties said his position as an MP was untenable.
Will Chris Pincher have the whip removed?
Despite quitting government, he still remains a Tory MP, with the party's whips office said to be considering whether he should be expelled.
Former ministers Caroline Nokes and Karen Bradley have written to Chief Whip Chris Heaton-Harris urging him to boot Mr Pincher from the party.
They ask for "a policy of zero tolerance" on sexual misconduct allegations and for each accused MP to be suspended from the party while they are investigated.
Several other Tory MPs have also been urging the party's whips to remove Mr Pincher, ITV News has been told, with at least one comparing him to shamed former Tiverton and Honiton MP Neil Parish who quit his seat after being caught watching pornography in Parliament.
Welsh Secretary Simon Hart refused to say his colleague should be booted from the party when talking to ITV News, but did suggest he could be removed by the end of today.
"I think it's absolutely right that the chief whip and others spend today just trying to ascertain exactly what happened, what the circumstances were, and therefore what to do next.
He added: "We have absolutely categorically have to stand back and assess every one of the facts and I don't think last night, I wasn't in a position at 8 o'clock last night when this information came through, to be able to make that objective judgement.
"Today is a day when the chief whip and others will be looking at all of the surrounding context of this and then deciding which way to go forward."
Asked why he was allowed to return to the role after previously quitting in similar circumstances, Mr Hart told ITV News that Mr Pincher went through the Cabinet Office vetting process and was given the "green light".
Labour deputy leader Angela Rayner hit out at Prime Minister Johnson over his failure to withdraw the Conservative whip from Mr Pincher.
"Boris Johnson and the Conservatives' failure to act just shows the rot that has set in at the heart of this Government.
"If this prime minister had an ounce of decency he would have already suspended the Tory Whip.
"It's now for the Conservative MPs who continue to prop up this prime minister's paralysed administration to step up, do the decent thing and show him the door."
Chris Pincher is just the latest Tory MP accused of sexually inappropriate behaviour
The Conservative party has been wracked by allegations of sleaze lately - the party lost two by-elections last week after the Tories who held those seats resigned over sexually inappropriate behaviour.
Neil Parish resigned as the MP for Tiverton and Honiton after being caught watching pornography in the Commons and Imran Ahmad Khan quit after being convicted of sexually assaulting a 15-year-old boy.
The allegations around Mr Pincher are yet another example of sleaze within the Conservative Party, explains Political Reporter Shehab Khan
What led to Mr Pincher quitting and what did he say in his resignation letter?
Christopher Pincher, MP for Tamworth, said he "embarrassed myself and other people" as he apologised to those concerned for the "upset" he said he had caused.
Complaints were made about him to Tory Party whips over his conduct at the Carlton Club, after he was reportedly seen touching two men inappropriately.
After being informed of the grievances, the deputy chief whip resigned and referred himself for investigation.
In his letter to Prime Minister Johnson, Mr Pincher 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 apologise 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.
"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 honour of my life to have served in Her Majesty’s Government."
Labour deputy leader Angela Rayner says the prime minister has "serious questions" to answer over why Mr Pincher "was given this role in the first place and how he can remain a Conservative MP."
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know
The MP for Tamworth was appointed alongside Chief Whip Chris Heaton-Harris last February to strengthen party discipline amid unrest among MPs over the way the government was being run, despite previously being accused of sexually inappropriate behaviour in 2017.
Having referred himself to both the police and the Conservative Party complaints procedure following an allegation he made a pass at Tory activist Mr Story, he was brought back by Theresa May as deputy chief whip in January 2018.
When Mr Johnson became PM in July 2019, Mr Pincher was moved to the Foreign Office as minister for Europe and the Americas before returning to the whips office for a third time in February 2021.
His departure comes just days after Oliver Dowden quit as party co-chair in the wake of the Wakefield and Tiverton and Honiton by-election losses.
It leaves Mr Johnson – who returned from the Nato summit on Thursday after nine days out of the country – with another headache with two crucial roles to fill.