But Mr Rees-Mogg tried to undermine the significance of Mr Ross’s call for the Prime Minister to step down by arguing that he was not a “big figure”. He claimed Mr Ross had always opposed Mr Johnson, despite the Scottish Tory leader backing him for the leadership.

Challenged about his comments on BBC’s Newsnight on Wednesday night, Mr Rees-Mogg doubled down, saying: “Douglas Ross has always been quite a lightweight figure.”

He refused to back down on Thursday and accused Mr Ross of disloyalty to the Prime Minister, saying: “If you take the king’s shilling, you are beholden to the crown.”

But Jamie Greene, the Scottish Tories’ shadow justice secretary, said the comments were “completely unnecessary” and Mr Rees-Mogg “should go and have a long lie down, maybe not in the House of Commons”.

Another Tory MSP said: “We don’t want to pick a fight with the UK party – that’s not what this is about. Douglas Ross is taking a principled and proper stand on a particular issue about Boris Johnson’s conduct.

“What purpose does it serve? He could have just said emotions are running high, he understands there are strong views, and we respect the position taken by colleagues.

“But to say what he said is bonkers. It is an absolute gift to our opponents, although one that’s somewhat diluted because it was Jacob Rees-Mogg who said it, who they spend their time mocking and deriding as a caricature and an irrelevance.”