Westminster’s expenses watchdog has suggested it cannot interfere with MPs' sleeping arrangements in its judgement on the so-called ‘SNP love-triangle’.

The Independent Parliamentary Standards Authority (IPSA) said it was not for it to "intrude on MPs’ private arrangements".

IPSA had been asked to look at the claims of SNP MPs Stewart Hosie and Angus MacNeil.

Both are said to have had affairs with political journalist Serena Cowdy, 36.

Reports suggest that Mr MacNeil conducted his relationship with Ms Cowdy at the Park Plaza hotel in London at the taxpayers' expense.

The SNP has always denied any financial impropriety, saying overnight guests create no extra cost for the public purse and MPs are not required to register them with IPSA.

In response, IPSA said that as MPs work in two places, parliament and their constituency, “we consider that it is appropriate for the taxpayer to fund accommodation in one of those locations.”

It added: “MPs are entitled to claim for accommodation costs in line with the (expenses) scheme, backed up with evidence. It is not for IPSA to intrude on MPs’ private arrangements.”

The complaint to IPSA was made by Labour MP Graham Jones, who asked for clarity around the rules.

In his letter to the body, set up in the wake of the 2009 expenses scandal, Mr Jones said that MPs “suffer enough criticism as it is. When rules are perceived to have been breached it is in everyone's interests to clarify matters."

Last week it emerged that a separate Parliamentary watchdog would not probe the expenses claims of the two MPs.

A spokesman for Westminster's Standards Commissioner Kathryn Hudson said that she had received a complaint but had decided not to begin an inquiry.

The issue was referred to Ms Hudson by the Scottish Conservative MSP Jackson Carlaw.

At the time the SNP described it as “no surprise that the Standards Commissioner has decided not to investigate Jackson Carlaw's complaint. It was a political stunt and a hypocritical move."

Mr MacNeil is reported to have had an affair with Ms Cowdy during the Scottish independence referendum.

Mr Hosie, who announced last month that he was separating from his wife, Scottish Health Secretary Shona Robison, resigned as the SNP's deputy leader 10 days ago.

First Minister Nicola Sturgeon denied that she had sacked him and said that he had done the "right thing" in stepping down.

She also described both Mr Hosie and his wife as "personal friends" and said they "now deserve the privacy to get on and get their lives on track".

Nominations for the party's new deputy leader do not close until August.