The PM, who is under pressure over Downing Street parties during COVID-19 restrictions in 2020 and 2021, said he would look at any evidence presented to him.

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William Wragg, chair of the public administration and constitutional affairs committee, said a "number of MPs have faced intimidation" in recent days after declaring, or assumed to have declared, their desire for a vote of confidence in Mr Johnson.

He told the committee it is "not the function" of the government whips office to breach the ministerial code by "threatening to withdraw investments in constituencies funded by the public purse".

He said the MPs who have been intimidated should contact the police.

MP who defected claims he was threatened

Christian Wakeford, the MP who defected from the Tories to Labour yesterday, said he was threatened by the whips. The Labour Party said it was over a vote on free school meals.

Mr Wakeford had been one of the Tory MPs who submitted a letter of no confidence in Mr Johnson and was said to have been "hauled" in by the Tory chief whip the night before he defected.

Whips 'blackmailing MPs and encouraging embarrassing stories'

Mr Wragg accused the whips of "encouraging the publication of stories in the press seeking to embarrass those that they suspect of lacking confidence in their prime minister".

He added that "intimidation of a member of parliament is a serious matter" and the reports he has been told of "would seem to constitute blackmail".

MPs who have been threatened with alleged blackmail should contact the Speaker of the House and the head of the Metropolitan Police, Dame Cressida Dick, Mr Wragg said.

Mr Wragg is one of a handful of Conservatives who have publicly called for Mr Johnson to go over the lockdown parties scandal, but he did not reveal if he had been intimidated or blackmailed by the whips office.

The PM said he had seen "no evidence to support any of those allegations" but "of course" he would look at any evidence presented to him.

'Mafia tactics'

Lib Dem MP Alistair Carmichael brought Mr Wragg's statement up in the Commons, saying he had had "never heard" of this type of behaviour before and said it was more the tactics of "the mafia" than parliament.

Speaker Sir Lindsay Hoyle replied by saying they are "serious allegations" and reminded whips they "are not above the criminal law" and any allegations should be investigated by the police, without his interference.

He warned it is "contempt to obstruct members in the discharge of their duty or to attempt to intimidate a member in their parliamentary conduct by threats".

There is a "clear process" for dealing with these matters, he said, as he told any MPs with concerns should write to him.

A Downing Street spokesman said: "We are not aware of any evidence to support what are clearly serious allegations.

"If there is any evidence to support these claims we would look at it very carefully."

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Former rival says PM has been 'badly wounded'

The accusation of threats comes as the PM faces a potential confidence vote in his leadership.

The threshold for triggering a contest has not yet been met, although some expect a Cabinet Office investigation into the partygate claims to potentially spark a flurry of letters from Tory MPs if the final report is critical of Mr Johnson.

MP Michael Fabricant, who earlier dismissed Mr Wragg's claims as "nonsense", told Sky News he fears the long-term impact of the current Tory divides over Mr Johnson's leadership.

"My worry is that when I became an MP from 1992 to 1997, there was a lot of loathing in the Conservative Party between those who had defended Margaret Thatcher and those who actually went out to knife her," he said.

"It does worry me that, stay or leave, the legacy of all this will be a deep scar in the body of the Conservative parliamentary party."

Speaking to Sky News, former Conservative MP Rory Stewart said he "can't see what future" the PM has.

"He may be able to survive for another few months, but he is badly wounded," said Mr Stewart, who stood in the Tory leadership contest won by Mr Johnson in 2019.

He said the PM's current predicament should not come as a surprise, adding: "He was manifestly unsuited to be prime minister from the beginning and it's very disturbing that a great country like Britain should have chosen somebody so unsuitable for the role."