The House of Commons standards watchdog has been asked to investigate the expenses of two SNP MPs involved in an alleged love triangle.
Jackson Carlaw, the deputy leader of the Scottish Conservatives, has written to Kathryn Hudson, the parliamentary commissioner for standards.
He has requested she look into claims made by Western Isles MP Angus MacNeil and SNP deputy leader Stewart Hosie.
His letter comes after reports suggesting journalist Serena Cowdy stayed with Mr MacNeil in a London hotel while the pair were allegedly having an affair.
Mr Carlaw said: “The SNP says there is no financial impropriety – but at the same time, it is widely reported that Mr MacNeil stayed with Ms Cowdy at a hotel in London and put the bill on expenses.
“The best course of action is for the UK Parliament’s standards commissioner to look into the matter.”
In his letter, he suggested the rules of conduct had been breached.
But an SNP spokeswoman said: “Angus MacNeil’s accommodation has nothing to do with it. To suggest any financial impropriety is totally wrong.”
First Minister Nicola Sturgeon has refused to be drawn on the issue, calling it a “private matter”.
Mr MacNeil, 45, announced his separation from his wife last year, while Mr Hosie, 53, and wife Shona Robison, Scotland’s Health Secretary, revealed on Sunday they were separating.
Newspaper reports have alleged Ms Cowdy – also reported to have had an affair with Mr Hosie – was a frequent guest of Mr MacNeil at the Park Plaza in Waterloo.
He chooses to stay in hotels while working in Westminster, renting out the flat he owns in the capital and claiming the cost of the hotels back in parliamentary expenses. MPs do not have to disclose details of any guests to the authorities.
Mr MacNeil was previously forced to pay back almost £900 in hotel expenses after exceeding the nightly rate set out under Independent Parliamentary Standards Authority (Ipsa) rules.
Mr Carlaw’s letter asks for both MPs’ expenses to be investigated, but no allegations have been made in respect of Mr Hosie, who was re-elected to his deputy post along with the other members of the Westminster group leadership on Tuesday night.