The Scottish Conservatives’ political opponents have called on them to hold Boris Johnson to account in a key Commons vote over whether he should face investigation over the partygate scandal.

The SNP and Scottish Labour have said Tory MPs should vote for the Privileges Committee to carry out an investigation to determine if Mr Johnson misled Parliament.

It comes after reports suggested Scottish Conservative leader Douglas Ross – who is both an MP and an MSP – will not be in Westminster for the vote on Thursday.

Mr Ross withdrew a letter of no confidence in the Prime Minister, saying the conflict in Ukraine made it important for him to remain in charge at Downing Street.

The SNP’s Westminster deputy leader Kirsten Oswald said her party would support the motion to refer the issue to the Privileges Committee.

She said: “Douglas Ross was previously quick to claim that ‘lying to Parliament and breaking the ministerial Code is a straight red, even in the most lenient referee’s book’ – now it seems as though he’s lost his cards.

“Ross has gone from running the line to running scared – attempting to dodge holding this law-breaking Prime Minister to account.

“Ross, along with the Scottish Tory MPs, must finally find a backbone, do the right thing and put the interests of the country ahead of the narrow interests of the Tory party.

“The reality is that Boris Johnson’s government is too engulfed in scandal to get on with the day job – with the Prime Minister and Chancellor too distracted to deal with the Tory cost-of-living crisis hammering households.”

Scottish Labour leader Anas Sarwar wrote to Tory MPs on the issue.

He said: “I was dismayed yesterday to hear that your party leader, Douglas Ross, has chosen that this issue is not important enough for him to vote on.

“The real judge of a politician’s character is what they do when what is right clashes with what is personally convenient for them.”

He continued: “The United Kingdom deserves better.

“So, on Thursday will you protect our Union or will you vote to save the skin of a man who is its greatest threat?

“The choice is a clear one. You are either on the side of doing what is necessary to protect the UK, or you are not.”

A spokesman for the Scottish Conservatives said: “As leader of the opposition in the Scottish Parliament, Douglas will be holding Nicola Sturgeon to account at First Minister’s Questions on Thursday.

“After FMQs he will be out on the doorstep campaigning ahead of the council elections, listening to the concerns of voters.”