Boris Johnson is "unfit for office", former Scottish Conservative leader Ruth Davidson has said.
The Prime Minister has been under mounting pressure in recent weeks over parties held in and around Downing Street during lockdown - one of which he confirmed he attended.
Baroness Davidson, who took her seat in the House of Lords last year after stepping down at Holyrood, was a vocal opponent of the Prime Minister's Tory leadership bid as well as being steadfastly against Brexit - a campaign led by Mr Johnson.
Speaking to the Times, she said if she was an MP, she would submit a letter of no confidence in the Prime Minister to the 1922 Committee - 54 of which are needed to trigger a vote on his leadership.
Baroness Davidson told the newspaper there is no "deep-rooted hatred" between the two, but she added: "I didn't support him for the leadership and I believe what has been exposed to have happened in the last few weeks shows that he's unfit for office but, I mean, he's perfectly convivial company."
As well as anger over the lockdown parties, Baroness Davidson claimed some in the Tory party are tired of the "drama" coming from Number 10.
"I think one of the reasons that the Prime Minister is in such a perilous situation is not just because of the apparent rule-breaking, although that is a big part of it, but because there is a fatigue even within the party and certainly by my MP colleagues for the drama that has been emanating from Number 10," she said.
The Prime Minister has struggled with support north of the border amid this most recent scandal, with current Scottish Tory leader Douglas Ross - along with most of his MSPs - publicly calling on him to leave.
Davidson's comments come as hundreds of pro-independence activists marched through Glasgow calling for the PM to resign.
The All Under One Banner march saw indyref2 supporters convene on George Square before making their way to Glasgow Green.
Recent polls have put support for independence on an equal standing with remaining in the United Kingdom.
Pollsters believe the scandals engulfing Downing Street are pushing some towards Scottish autonomy.
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