Aaron Bell, the Conservative MP for Newcastle-under-Lyme, has confirmed he has submitted a letter of no confidence in the Prime Minister Boris Johnson.
In a tweet, Mr Bell said he was "profoundly disappointed" to have done so.
"The breach of trust that the events in No 10 Downing Street represent, and the manner in which they have been handled, makes his [Boris Johnson's] position untenable.
"I believe it is in the country's best interests that this matter is resolved as soon as possible."
His letter has been handed in to Sir Graham Brady, the Chairman of the 1922 Committee of Tory MP's.
If he were to receive fifty-four letters, a vote of no confidence in the Prime Minister would be called.
At the beginning of the month Mr Brady told ITV Central Political Correspondent, Alison Mackenzie, that he had "serious problems" with Downing Street's leadership.
ITV Central Political Correspondent Alison Mackenzie spoke to Aaron Bell on the 1st of February, the day after Sue Gray's interim findings were published
"I think there has been a real breach of trust - not just with Conservative MPs but with ordinary, decent people who followed the rules and obeyed the rules," he said at the time, expressing his disappointment at alleged breaches of lockdown restrictions at No 10 during the pandemic.
Why are MPs submitting no-confidence letters?
The past few weeks have seen a number of allegations levelled at No 10 Downing Street.
Multiple reports have alleged that parties were held on various occasions at times when the country was in lockdown.
Twelve such events are now being investigated by the Metropolitan Police.
On January the 31st Sue Gray, a senior civil servant, published her interim report into the events, finding that there had been "failures of leadership and judgement" in No 10.
She criticised the culture in Downing Street and said that the social gatherings in question were "hard to justify" under then lockdown rules.
Pressure has increased on the Prime Minister over the past 48 hours, after he claimed in the House of Commons that the Leader of the Opposition, Sir Keir Starmer, had failed to prosecute Jimmy Saville when he was Director of Public Prosecutions.
The accusation sparked widespread criticism, and led to the resignation of policy chief Munira Mirza this morning. Four other advisors also resigned - although No 10 has said that three of these were planned departures.
Who is Aaron Bell?
Aaron Bell has been the MP for Newcastle-under-Lyme in Staffordshire since 2019.
On Wednesday, during a turbulent Prime Minister's Questions, he reflected on the loss of his Grandmother in May 2020, and the fact he had been unable to spend time with family members after the funeral in order to comply with lockdown regulations.
"I didn't hug my siblings, I didn't hug my parents," he said.
"I gave the eulogy and then, after that, I didn't even go to her house for a cup of tea. I drove back, three hours, from Kent to Staffordshire.
"Does the Prime Minister think I'm a fool?"
Civil servant Sue Gray is now leading an investigation into what happened and a criminal inquiry has been launched by the Met Police.
Boris Johnson has apologised for his presence at an apparent 'bring your own booze' party in the Downing Street garden, but said he believed in was a work event.
When contacted for comment No.10 Downing Street pointed us towards Mr Johnson's statement at PMQ's when he apologised and said,
"I know that millions of people across this country have made extraordinary sacrifices over the last 18 months.
"I know the anguish that they have been through, unable to mourn their relatives and unable to live their lives as they want or to do the things they love.
I know the rage they feel with me and with the Government I lead when they think that in Downing Street itself the rules are not being properly followed by the people who make the rules."