Speaking as he returned to the campaign trail after announcing he will step down as Scottish Tory leader following the election, he said he was “very comfortable for that to be investigated”.

It was reported on Sunday that Mr Ross had billed the public purse for flights between London and Glasgow or Edinburgh, where he was officiating at football matches, rather than for returning to his Moray constituency.

Ipsa said MPs were “normally” expected to travel from their nearest airport, which for Mr Ross would have been Inverness, “but they can also claim for extended UK travel or diverted travel”.

Although Mr Ross dismissed the content of the story, his allies said the fact that the allegations had been briefed from within the Scottish Tories contributed to his announcement on Monday he was quitting.

He had already faced a fierce internal backlash against the party’s decision to deselect David Duguid, a former minister, as its candidate for Aberdeenshire North and Moray East and install Mr Ross instead.

Mr Duguid has vehemently denied the Tories’ claim he was too ill to fight the seat after being in hospital for weeks with a serious spinal condition.

‘Comfortable for claims to be investigated’

Speaking at a campaign stop in Edinburgh, Mr Ross, who is a professional assistant referee, said: “I am very confident that the claims I have made have been in line with my duties as a Member of Parliament and travelling to and from Westminster. But what I also said is I am very comfortable for that to be investigated.”

He added: “As a Member of Parliament, sometimes I’ve travelled from Inverness, sometimes from Aberdeen, sometimes from Edinburgh, sometimes from Glasgow. But they are always in line with getting to and from the House of Commons.”

An Ipsa spokesman said: “We are currently reviewing the information that has appeared in a number of articles over the weekend. If there is evidence of any rules within the scheme being broken, we will work with the former MP to clarify the situation.

“If it is necessary, we are also able to refer matters to the compliance officer for Ipsa for investigation.”

She said the rules “vary on a case by case basis” and “there are multiple reasons why an MP may need to claim for an extended travel which would see them submit an eligible claim for a journey that isn’t to their nearest airport or train station, for instance”.

Keith Brown, the SNP’s depute leader, wrote to Ipsa demanding an inquiry and arguing that Mr Ross using public funds for travel for his refereeing duties would breach the MPs’ code of conduct.

He said: “If these allegations were fully substantiated, it would mean that Mr Ross has been abusing his public funded Westminster expenses to unfairly fund his receipt of another, separate salary.

“It would amount to another Westminster expenses scandal carried out by the current leader of the Scottish Tory Party.”

Resignation ‘poorly timed’ 

Mr Ross announced on Monday that it was “not feasible” for him to remain leader while being an MP and MSP. He also said he would quit Holyrood if he was elected an MP on July 4.

Tory MSPs were bemused and upset by the timing of his decision, saying the furore over Mr Duguid was not being raised by voters on the doorsteps and Mr Ross was under zero pressure to resign.

Asked if he would apologise to Scottish Tory voters for the “farce of the last few days”, he said: “Yeah, I’m sorry this has not been good enough. It’s not how I planned the campaign.

“I didn’t expect to be announcing that I would be standing down during the middle of the campaign. But I had to take a decision reflecting on what colleagues and others have said.”

Mr Ross said some in his Holyrood group had raised “legitimate concerns” about him potentially being an MP and MSP at the same time and the decision was not “universally popular”.

However, he said he would continue fronting the Scottish Tory campaign, including appearing in a BBC leaders’ debate on Tuesday night.

Mr Ross also denied giving himself “job insurance” by pledging to stay on as a Highlands and Islands MSP if he fails to be elected to Westminster.

When he was crowned Scottish Tory leader in Aug 2020, he was Moray MP but was elected an MSP in the following year’s Holyrood election.

At the time, he pledged to stand down as an MP at the next general election so he could focus on the 2026 Holyrood contest and the battle to become First Minister.

But he performed an about-turn last Thursday, despite his Moray Westminster seat being abolished following boundary changes. About a third has been absorbed into the new Aberdeenshire North and Moray East constituency.