Sir Gavin Williamson has quit Rishi Sunak’s Cabinet after conceding that allegations about his conduct had become a “distraction”.

The former Cabinet Office minister said he had decided to “step back from Government” while the complaints process into his conduct is carried out, vowing to “clear my name of any wrongdoing”.

The decision to quit follows allegations he sent expletive-laden messages to former chief whip Wendy Morton complaining about being refused an invitation to the Queen’s funeral, claims he bullied a former official at the Ministry of Defence and an accusation of “unethical and immoral” behaviour while he was chief whip.

Sir Gavin said there was an ongoing complaints process “concerning text messages I sent to a colleague” – a reference to Ms Morton’s complaint.

“I am complying with this process and I have apologised to the recipient for those messages,” he said.

“Since then, there have been other allegations made about my past conduct. I refute the characterisation of these claims, but I recognise these are becoming a distraction for the good work this Government is doing for the British people.

“I have therefore decided to step back from Government so that I can comply fully with the complaints process that is underway and clear my name of any wrongdoing.“

Sir Gavin quit following a meeting with the Prime Minister on Tuesday evening.

In his response, Mr Sunak said he was accepting the resignation “with great sadness”, but “I support your decision to step back and understand why you have done it”.

He told Sir Gavin “I would like to thank you for your personal support and loyalty” and expressed his “gratitude for the work you have done for this government”.

The flurry of accusations against Sir Gavin had triggered a series of investigations by the Tory party, the Commons bullying watchdog and an informal fact-finding exercise by No 10.

His resignation came just hours after Downing Street insisted Mr Sunak still had full confidence in the minister.

Pressure on Sir Gavin – and questions over Mr Sunak’s judgment – began with the publication of messages he sent Ms Morton, and the revelation that the Prime Minister was informed of a complaint against him when he appointed his Cabinet.

As well as the internal Tory investigation, she is also understood to have referred the case to Parliament’s bullying process.

In a series of texts peppered with swear words, Sir Gavin accused Ms Morton of seeking to “punish” MPs out of favour with then-premier Liz Truss by excluding them from the Queen’s funeral, warning: “There is a price for everything.”

Another complaint to Parliament’s Independent Complaints and Grievance Scheme (ICGS) has reportedly been made by a former senior official who worked with Sir Gavin when he was at the Ministry of Defence.

He is alleged to have told the official to “slit your throat” and on a separate occasion told them to “jump out of the window”, according to a Guardian report.

The former official did not complain at the time but has now gone to the ICGS, claiming the alleged bullying had taken “an extreme impact” on their mental health.

On Tuesday night, former deputy chief whip Anne Milton alleged Sir Gavin used intimidatory and threatening tactics while he was chief whip.

She accused him of seeking to use an MP’s financial situation as leverage against them and sending an expletive-laden email about a female civil servant.

Ms Milton, who was deputy chief whip from May 2015 to June 2017, described his behaviour as “unethical and immoral”, claiming: “I think he feels that he’s Francis Urquhart from House Of Cards.”

Ms Milton, who was stripped of the Tory whip during the Brexit rows in 2019 and subsequently lost her seat, told Channel 4 News: “I got the impression that he loved salacious gossip, and would use it as leverage against MPs if the need arose.”

She told the broadcaster that Sir Gavin had a rant about civil servants in 2016 in response to a female official asking why a minister had to change travel plans for a vote.

“Always tell them to f*** off and if they have the bollocks to come and see me,” he said in an email, according to Ms Milton.

“F****** jumped up civil servants.”

She said that when the whips’ office gave some financial assistance to an MP, Sir Gavin told her that when she handed over the cheque she should make sure “he knows I now own him”.

She questioned Mr Sunak’s decision to give Sir Gavin a ministerial job, saying: “I think (at) best it was probably a bit naive.”

Sir Gavin, who was knighted after being nominated for the honour by Boris Johnson earlier this year, is a divisive figure at Westminster, where he is viewed with suspicion by many Tory MPs because of his reputation as an inveterate plotter.

He was sacked first by former PM Theresa May as defence secretary in 2019 for leaking details of a National Security Council meeting, and then by Mr Johnson as education secretary over the Covid-19 A-levels debacle.

However, he was regarded as a key figure in Mr Sunak’s campaign over the summer to become party leader and his departure will be embarrassing for the Prime Minister.

Mr Sunak will face MPs at Prime Minister’s Questions on Wednesday and Sir Gavin’s decision to resign could help him avoid some of the inevitable attacks coming his way.

But deputy Labour leader Angela Rayner said: “This is a damning reflection of a weak Prime Minister. Rishi Sunak appointed Gavin Williamson with full knowledge of serious allegations about his conduct and repeatedly expressed confidence in him.

“This is yet another example of Rishi Sunak’s poor judgement and weak leadership.”

She claimed Mr Sunak was “trapped by the grubby backroom deals he made to dodge a vote” on the leadership.

“As families struggle during a cost of living crisis made in Downing Street, yet another Tory government has descended into chaos.”

Liberal Democrat deputy leader Daisy Cooper said: “This should be the third and final time Gavin Williamson is forced out of the Cabinet.

“Rishi Sunak has serious questions to answer about why he appointed Gavin Williamson, then stood by him instead of sacking him.

“His promise to lead a government of integrity has now been left in tatters.”