Scotland’s First Minister has said an independent inquiry should be launched into allegations that Tory MPs calling for the Prime Minister to quit have faced blackmail and intimidation.

William Wragg, chairman of the Commons Public Administration and Constitutional Affairs Committee, said he has received reports of conduct amounting to “blackmail”.

He said they include “members of staff at 10 Downing Street, special advisers, Government ministers and others encouraging the publication of stories in the press seeking to embarrass those they who suspect of lacking confidence in the Prime Minister”.

Nicola Sturgeon called for an inquiry to be launched, while Scottish Conservative leader Douglas Ross – who has called for the Prime Minister to resign over the Downing Street parties scandal – said he is disappointed in the allegations but has not experienced any intimidation himself.

Ms Sturgeon told ITV Border as she entered the Holyrood chamber ahead of First Minister’s Questions on Thursday: “These are gravely serious allegations – intimidation, blackmail and using public money to do it.

“I would suggest that these accusations need to be fully and, crucially, independently investigated.

“With everyday right now, Boris Johnson is tarnishing the office of Prime Minister and I think if he has concerns for the interests of the country, he will go.”

When asked if the allegations surprise her, the First Minister responded: “They shock me.”

Douglas Ross in Holyrood
Douglas Ross last week called for the Prime Minister to step down (Fraser Bremner/Daily Mail/PA)

Later, the First Minister said in a tweet that if the allegations are found to be true, they amount to “corruption”.

She wrote: “Let’s be clear: if Tories are threatening to withhold public investment from constituencies as a way of keeping MPs in line then, yes, that’s blackmail & intimidation – but it is also corruption.

“The moral decay at the heart of Johnson’s govt may be even worse than we thought.”

Mr Ross, meanwhile, said he has not heard from MP colleagues who claim to have been intimidated, adding: “I’ve refereed Buckie v Deveronvale (and) Wick v Brora, so I don’t think people would try and intimidate me, those games certainly didn’t, and nobody in Government has tried to do that either.”

He added: “I think anyone in the Conservative Party would be disappointed to hear these allegations and it’s right that they are properly investigated.”