Scottish Secretary Alister Jack has said he will support the Prime Minister in a confidence vote.

The threshold of 54 MPs submitting letters to the backbench 1922 Committee to force a vote on Boris Johnson’s leadership was passed on Sunday, chairman Graham Brady said.

With a secret ballot of MPs scheduled for Monday evening, ministers and other MPs have been voicing their support for Mr Johnson as pressure continues to mount in the wake of the Sue Gray report.

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.”

The spotlight now falls on Scottish Tory leader Douglas Ross, who was among the most senior Tories calling for the Prime Minister’s resignation at the turn of the year when reports of parties in Downing Street during lockdown surfaced.

Mr Ross eventually reversed course, citing the Russian invasion of Ukraine and the need for stability at the top of government to deal with the situation.

One of Mr Ross’ senior Tory MSPs – former leadership candidate Murdo Fraser – was the first among 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.”

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

In the correspondence sent directly to Mr Johnson, the MP 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 also piled on the pressure, saying: “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.”