Scottish Tory leader Douglas Ross will vote against the Prime Minister in Monday’s confidence ballot.
In a statement released on social media, Ross said he “cannot in good faith” support Boris Johnson and will support a motion of no confidence in the PM.
Conservative MPs will vote to decide on Johnson’s future on Monday evening.
“While war in Europe continues and the UK Government is providing such strong support to President Zelenskyy and the people of Ukraine, the timing of this vote is far from ideal,” Ross said.
“However, while I’ve not sought to bring this vote about at this time, it is now going ahead tonight, and I’ve had to consider how to vote on behalf of my constituents and the country.
“I do so knowing there are vocal opinions on both sides of this argument, an argument that has dominated much of the political discussion for many months.”
Ross said that he had “listened closely” to his constituents and people living across Scotland as he made his decision.
He continued: “The Prime Minister can be proud of many of the successes his government have led on, particularly the Covid vaccine and the furlough scheme.
“However, 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.
“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.”
Conservative councillor Marc Macrae, the convener of Moray council, welcomed the party leader’s announcement.
He said: “The Prime Minister finds himself in an untenable position and it is clear that whilst he might retain the confidence of some Conservatives, he has lost that of the general public and a considerable percentage of his own party.
“I welcome the announcement from Moray’s MP Douglas Ross that he fully supports this evenings motion of no confidence in Mr Johnson and hope that we can see an end to this matter, one which is clearly distracting from the need to govern the UK effectively at a very challenging time.”
Co-leader of Moray council, Councillor Neil McLennan added: “Humans are fallible. The breaking of rules is one thing, but untruths, double standards and cover-ups are what really stick in the craw of the electorate.
“Whilst there are many opinions on both sides of the argument we cannot allow this to become the sole focus of our parliament. The public at large have very much made their feelings known across the UK and tonight MP’s will vote on the matter. That is democracy.”
Following the Scottish Conservative party leader’s announcement, three more Scottish Tories confirmed that they had voted against Johnson in the no confidence vote.
Tory MP and former Scotland Secretary David Mundell tweeted: “After a difficult couple of years and listening to the views of my constituents, I voted tonight for a fresh start and new leadership for our country.”
Andrew Bowie, Tory MP for West Aberdeenshire and Kincardine, said he made the “extremely tough decision” to vote against the Prime Minister.
He said: “Tonight, and with a heavy heart, I have taken the extremely tough decision to vote against the Prime Minister.
“I have not taken the decision lightly, at all, but after listening to my constituents.
“They remain understandably angry and upset at what has happened, this was the only choice for the good of the country.”
John Lamont MP confirmed his no confidence vote and resigned as the parliamentary private secretary to Liz Truss.
In a statement, he said: “I have consulted widely with my constituents in the Scottish Borders, I’ve also received thousands of emails and had countless conversations about the Prime Minister’s performance over the last few weeks and months.
“The events in Downing Street during the lockdown were unacceptable. People across the country have been rightly deeply angered by what went on.
“Whilst I recognise that changes have been made in Downing Street, the unfortunate reality is that the government has become overwhelmed by these events, to the detriment of my constituents and people across the United Kingdom.”