The Tory chief whip at Holyrood has said there is now an “inevitability” to Boris Johnson having to leave office as a result of the partygate scandal.

Stephen Kerr predicted a no confidence vote in the Prime Minister after next week’s report into Downing Street parties during the pandemic lockdown, and that regardless of the result the PM would go.

Mr Kerr, a former Stirling MP who is now a Central Scotland list MSP, made the comments on the BBC’s Sunday Show.

Mr Kerr also said reports of bullying and intimidation by Tory whips at Westminster would be “totally unacceptable” if true, and said there should be an inquiry into it.

He said: “I am shocked. That is not how we can conduct any business in the 21st century.”

Asked if there was now “civil war” in the Tory party, Mr Kerr did not deny it, but said the situation was “not very good”.

Asked if he could see Mr Johnson surviving next week’s partygate report by ethics mandarin Sue Gray, Mr Kerr said: “No. I think the longer it takes for the Sue Gray report, the more detail there’s going to be in it, the more investigation will have taken place.

“I think there’s an inevitability to what happens next. 

“It gives me absolutely, as you can imagine, no joy whatsoever to talk about a Conservative Prime Minister having to leave office, but I think that is where this ends up.”

He said that after the report emerged, he expected Tory MPs to secure a no confidence vote in the PM by writing to Sir Graham Brady, the chair of the backbench 1922 committee.

“Regardless of the outcome of that vote, as we saw with Theresa May, there’s an inevitability of what follows.”

Mrs May won a no confidence vote led by Brexiteers in November 2018 by 200 votes to 117, but was still gravely damaged, and quit six months later after the May 2019 Euro elections.

Scottish Tory leader Douglas Ross last week called for Mr Johnson to quit over the scandal, while former leader Ruth Davidson said the PM was “unfit for office”.

Asked if Mr Johnson surviving would make Mr Ross’s position “unsustainable”, Mr Kerr insisted his position was actually “unassailable” and he would be staying out. 

Despite Mr Ross becoming leader unopposed in August 2020, Mr Kerr said: He said: “I can state absolutely categorically that Douglas Ross’s mandate comes from the Scottish Conservative party and its membership. It’s a completely separate issue. 

“Douglas is staying put. Douglas is there for good. Douglas is doing a great job. It’s Douglas Ross’s principled leadership that is, I think, shining a very bright light on all of this.”

Asked if Mr Ross could campaign for Mr Johnson if he was still PM at the next general election, Mr Kerr said: “There’s a lot of ifs in that question, and as I’ve already said I think there’s an inevitability to this process which results in a change of leader of the UK Conservative leader and a change of Prime Minister.”

Mr Kerr also said there was “no discussions whatsoever at any level” in the Scottish Tiory leadership about a breakaway Scottish party quitting the UK Tories.