Scottish Tory leader Douglas Ross will vote to remove the Prime Minister in a confidence vote on Monday.

Boris Johnson’s fate will be decided by Conservative MPs after a slow trickle of letters to the backbench 1922 Committee triggered a ballot on his leadership.

Mr Ross waited until Monday afternoon to publicly state his position, almost nine hours after the vote was announced, reversing his previous support for the Prime Minister to remain, in order to provide stability at the top of government during the Russian invasion of Ukraine.

But he has returned to his original view in light of the initial partygate allegations, saying he “cannot in good faith support Boris Johnson”.

“I have heard loud and clear the anger at the breaking of Covid rules that we all did our best to follow, and even more so at the statements to Parliament from the Prime Minister on this topic,” he said in a statement.

“Having listened closely to people in Moray who re-elected me to represent them, and from many people across Scotland, now that this confidence vote is upon us, I cannot in good faith support Boris Johnson.

“My vote tonight will support the motion of no confidence.”

Despite saying he would vote against the Prime Minister, Mr Ross added that he “can be proud of many of the successes his government have led on, particularly the Covid vaccine and the furlough scheme”.

It has been almost two weeks since the Moray MP told the PA news agency that the Prime Minister should continue in office, after the Sue Gray report found that “senior leadership” within Number 10 should “bear responsibility” for the culture which led to parties being held during 2020 and 2021.

Earlier in the day, Scottish Secretary Alister Jack voiced his support for the Prime Minister.

Mr Jack, unlike others in the Scottish Tories, has been steadfastly behind the Prime Minister throughout his tenure.

“The Prime Minister has my full support, and I will be voting to back him tonight,” he said on Monday.

“He is showing tremendous leadership as we face major challenges at home and abroad.

“I have no doubt that my colleagues in the Parliamentary party will vote to show their confidence in the Prime Minister.”

One of Mr Ross’ senior Tory MSPs, former leadership candidate Murdo Fraser, was the first in the Scottish party to speak out on the issue, saying the country should have a “fresh start” under a new leader.

“I don’t have a vote in tonight’s ballot in the House of Commons, but if I did I would be voting for change, and I would urge MP colleagues to vote accordingly,” he said on Twitter.

“The country needs a fresh start under new Conservative & Unionist leadership.”

He was followed by MSPs Douglas Lumsden and Jamie Greene, who hinted at their lack of support for the Prime Minister on Twitter.

Meanwhile, one of Mr Ross’s predecessors, Baroness Ruth Davidson, shared a letter from Tory MP Jesse Norman to the PM, stressing “how right (Mr Norman) is”.

In the letter Mr Norman described the plan to send some asylum seekers to Rwanda as “ugly”, plans to change the Northern Ireland Protocol as “economically very damaging, politically foolhardy and almost certainly illegal” and accused the Prime Minister of presiding “over a culture of casual law-breaking”.

SNP Westminster leader Ian Blackford said: “Tory MPs must finally put the interests of the public first. They must vote Boris Johnson out and do it now.

“And there cannot be any more flip-flopping from Douglas Ross and the Scottish Tories.

“Ross has made himself and the Tory Holyrood group look utterly ridiculous, while the rest of the spineless Scottish Tory MPs have shown nothing but craven loyalty to Boris Johnson – it is way past time for all of them to finally do the right thing and vote him out of office.”

Scottish Labour leader Anas Sarwar said Tory MPs should remove the Prime Minister or voters should do so at the next election, adding: “Douglas Ross pretends to be the great defender of the United Kingdom but everyone knows that Boris Johnson is a disaster for the UK and a gift to those who wish to break the UK up.

“Today, Douglas Ross and his Scottish Tory MPs have a choice. Are they on Boris’s side or Britain’s?

“Just like Boris Johnson, Douglas Ross’s leadership is over – standing up to Boris is his last roll of the dice.”

Scottish Government minister and Greens co-leader Patrick Harvie said: “It’s time for Douglas Ross, and his colleagues at Westminster, to finally do the right thing and bring an end to Boris Johnson’s utterly inept premiership.

“It is clear to the country that Boris Johnson should go, but realistically we can’t expect any kind of principled outcome today.”

Scottish Lib Dem leader Alex Cole-Hamilton said: “The rest of the country knew Boris Johnson had to go months ago.

“Douglas Ross and other MPs have lacked the courage or decency to remove him.

“If they support a law-breaking and lying Prime Minister tonight then they will be insulting everyone who made sacrifices during the pandemic.”