A second watchdog has been urged to investigate the conduct of two SNP MPs in relation to their accommodation expenses amid allegations of affairs.

Labour MP Graham Jones has made a complaint about Angus MacNeil and Stewart Hosie to the Independent Parliamentary Standards Authority (Ipsa).

Scottish Conservative deputy leader Jackson Carlaw has also written to parliamentary standards commissioner Kathryn Hudson claiming Mr MacNeil and Mr Hosie, the SNP's deputy leader, may have ''fallen short'' of the MPs' rules of conduct.

The SNP has said any suggestion of financial impropriety in relation to the MPs' expenses is ''totally wrong''.

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The complaints relate to reports both men had affairs with Westminster journalist Serena Cowdy.

The Daily Mail has alleged Ms Cowdy was a frequent guest of Mr MacNeil, 45, at the Park Plaza in Waterloo - a hotel often used by the Western Isles MP.

Mr MacNeil chooses to stay in hotels while working in Westminster and rents out the flat he owns in the capital. He claims the cost of the hotels back in parliamentary expenses.

The Herald:

Mr Hosie, 53, who is also reported to have had a relationship with Ms Cowdy, claims expenses on a flat in London.

Mr Jones is understood to have written to Ipsa, the body created to independently oversee MPs' expenses, asking it to look into the claims "to ensure that the expenses system has not been compromised".

A Labour spokesman said: "There are serious allegations here about a potential misuse of taxpayer funds by senior SNP MPs. It is right that these allegations are fully investigated."

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The office of the parliamentary standards commissioner said Mr Carlaw's correspondence had not yet been received while Ipsa confirmed it had received an email in relation to the two MPs which would be considered.

Mr MacNeil announced his separation from his wife last year while Mr Hosie and wife Shona Robison, Scotland's Health Secretary, announced on Sunday they were separating.

In a statement, Mr MacNeil said: "My accommodation in London is claimed under normal expenses, as is the case for all MPs, and the cost of this is compliant with the rules of the Independent Parliamentary Standards Authority (Ipsa).

"I don't like to comment on my personal life or related tabloid stories, but my marriage sadly ended for very different reasons to what has been suggested in lurid newspaper stories this week."

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First Minister and SNP leader Nicola Sturgeon told the BBC she had "seen no evidence of any breach of parliamentary expenses rules".

She said: "Ultimately, of course, that's a matter for the parliamentary authorities to determine. Beyond that, these are matters that are private and personal matters."

An SNP spokeswoman said: "The expenses were approved by the Commons authorities in line with the rules on MP's London accommodation and none of them involved any additional cost to the public purse beyond that."