Nicola Sturgeon asked how Scottish Tory leader Douglas Ross can “look himself in the mirror” after he used the Ukraine war as an excuse to back Boris Johnson.
The first minister branded him the “lowest of the low” for claiming the eastern European conflict meant it would be irresponsible to remove the Conservative chief from power.
Mr Ross called on the prime minister to quit over the partygate scandal in January but backed down following Vladimir Putin’s invasion.
Earlier this week he continued to insist Boris Johnson should not stand down despite receiving a fine for breaking lockdown.
The prime minister, his wife and Chancellor Rishi Sunak were all given fixed penalty notices for attending a birthday event for him in June 2020 while the nation stayed at home.
Mr Ross insisted Mr Johnson is a “truthful man” even though he denied in December any restrictions had been breached at the heart of government.
But Nicola Sturgeon later said it was shameful for Tories to use the Ukrainian conflict as a reason to keep the prime minister in office.
The SNP leader told Bauer Media: “Douglas Ross has in some ways been leading that particular line and how he can look himself in the mirror in doing so, let alone look anybody in Scotland in the eye, is beyond me.
“At a time of real serious issues for the UK to confront, surely it’s all the more important that the incumbent in No10 is a prime minister who can lead with moral authority?”
She added: “The Tories are refusing to abide by these long-established, accepted norms of democracy.
“They’re using their majority in the House of Commons to ride roughshod over the normal operation of democracy.
‘Complicit’
“Every time they turn a blind eye to the misconduct of Boris Johnson they become complicit in all of this.”
Mr Ross had said: “While I share the anger and the fury that people have about this now, and people have had about this for months, I’m also looking at the global situation.
“I think even the prime minister’s harshest critics would agree that he and the UK Government have responded well to the situation in Ukraine.”
But former Holyrood Tory leader Ruth Davidson continued to demand the prime minister’s resignation.
Mr Ross has previously admitted fallout from the partygate scandal could damage Tory hopes during the upcoming local elections.