THE Commons bullying watchdog has been asked to investigate one of Rishi Sunak’s most controversial cabinet ministers amid growing questions about the Prime Minister’s judgment.

Sir Gavin Williamson, who Mr Sunak appointed to the Cabinet Office last month knowing he was the subject of an official party complaint, has now been reported under a new procedure.

Former Chief Whip Wendy Morton has asked the Parliament’s Independent Complaints and Grievance Scheme after the Times reported she feared a “whitewash” by the Tory party.

Sir Gavin sent Ms Morton a series of expletive-laden texts accusing her of trying to “punish” MPs out of favour with then PM Liz Truss by excluding them from the Queen’s funeral.

He said Ms Morton was trying to “f*** us all over”, adding: “There is a price for everything”.

Scottish Tory leader Douglas Ross has said he would have sacked any of his front bench who used such language to a colleague.

Mr Sunak said the language was "not acceptable", but No10 later insisted the Prime Minister still had full confidence in him.

Ms Morton’s referral to the Commons watchdog coincided with yet more allegations of bullying and intimidation by Sir Gavin.

The Guardian reported that in his former role as Defence Secretary, he told a senior civil servant to “slit your throat” and “jump out of the window”.

The allegations, including that Sir Gavin “deliberately demeaned and intimidated” the civil servant on a regular basis, will add to the calls for his sacking.

Downing Street said it treated the latest allegation as “serious” and was looking into it.

The Prime Minister’s official spokesman said: “There have been further allegations reported this morning. Those are serious allegations that have come in.

“It’s true that no formal complaint has been made but we want to consider proper processes before commenting further.”

It was unclear how the UK Government would investigate, but the Cabinet Office’s Propriety and Ethics team would be one option for handling a complaint.

In a statement, Sir Gavin said: “I strongly reject this allegation and have enjoyed good working relationships with the many brilliant officials I have worked with across Government.”

Downing Street did not say whether Mr Sunak had set up any meetings with Sir Gavin, who holds the vague brief of “minister without portfolio” in the Cabinet Office.

The Prime Minister has come under sustained pressure over his decision to bring his ally back into Government despite knowing about a complaint made by Ms Morton.

Labour Party chair Anneliese Dodds said Ms Morton's decision to report Sir Gavin to the ICGS showed a "lack of faith in the Conservative Party complaints process".

She said: "The buck stops with Rishi Sunak. He was warned about Gavin Williamson's behaviour and appointed him anyway."

The Liberal Democrats demanded an independent inquiry into Sir Gavin’s conduct so the Tories do not “mark their own homework”.

Cabinet Office spokeswoman Christine Jardine said: “Anything less would be an abdication of leadership from No 10, and make a mockery of Sunak’s promise to govern with integrity.

“The findings must be made public – if the Conservatives have nothing to hide, they have nothing to fear.”

Work and Pensions Secretary Mel Stride said it would be “utterly, utterly unacceptable” if Sir Gavin Williamson had told a senior civil servant to “slit your throat”, but also insisted the report was in the “realm of media speculation”.

Mr Stride said: “There is an independent inquiry, as you know, going on around another … alleged incident between himself and the then-chief whip Wendy Morton.

“I think the important thing we do now is not to start intervening … and opining on who’s right and wrong or what may or may not have happened, but to wait for the results of that investigation.

“And then when we have that, and any other investigation that may be triggered in the meantime, then I think we can take stock and come to a firm conclusion.”

Any investigation could take several weeks, with Mr Stride suggesting Sir Gavin will still be in post by Christmas as any process “will take some time and we’ve got to wait to see what comes out of that”.

Mr Stride, who spoke of an “aura or mystique around” Sir Gavin, said that no minister was “unsackable”.

Shadow home secretary Yvette Cooper accused the prime minister of making “grubby political deals that aren’t in the national interest” to appoint Sir Gavin and Suella Braverman.

Sir Gavin, who was sacked as defence secretary in 2019, issued a statement denying the broad allegations in The Guardian’s report but did not specifically deny using the language alleged.

“I strongly reject this allegation and have enjoyed good working relationships with the many brilliant officials I have worked with across government,” he said.

“No specific allegations have ever been brought to my attention.”

The paper said the official, who later left government, complained to the MoD’s head of human resources about the alleged incidents.

A Cabinet Office spokesman said: “The Cabinet Office has not received notice of any formal complaints about Gavin Williamson’s behaviour from his time at the Ministry of Defence or any other department.”

Former Tory cabinet minister Baroness Morgan said she had “run-ins” with Sir Gavin when he was Theresa May’s chief whip, adding: “None of this surprises me, sadly.”

She told TalkTV on Monday: “Unfortunately Gavin has a reputation, it’s not a very nice one, and I really don’t know why Rishi Sunak felt he had to have him back in Government.”

Sir Gavin, who was knighted 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 Theresa May as defence secretary 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.