SNP MPs have hit out after Conservatives including the Prime Minister mocked the affair allegations surrounding the party.

Cabinet minister Chris Grayling was among those who joked in the Commons about reports that SNP MPs Angus MacNeil and Stewart Hosie both had affairs with political journalist Serena Cowdy, 36.

Two Westminster watchdogs have been asked to probe the MPs' expenses amid claims Mr MacNeil took Ms Cowdy to the Park Plaza in London’s Waterloo, where he stayed at the taxpayers’ expense.

Read more: Nicola Sturgeon drawn into SNP love triangle

The SNP insist that claims of financial impropriety are “totally wrong”.

The party says that MPs are not required to register overnight guests and that there is no extra cost to the taxpayer.

Commons leader Mr Grayling joked to MPs that there must be "something in the water" in Scotland.

The Herald:

He also said that he was reconsidering advice from Mr MacNeil about when to "put the ram in with the ewes".

Earlier in the week David Cameron also told MPs: "I know the SNP has other things on their mind... I think it's mostly the same thing."

One SNP MP attacked the comments as “outrageous”.

Another accused the Conservatives of hypocrisy for asking Westminster’s standards commissioner to look at expenses claims.

“Are the Conservatives also planning to put spies in the bedroom of every Tory MP?” he said.

Read more: SNP love triangle - second watchdog urged to investigate MPs' expenses

Labour MP Graham Jones has also made a complaint to the Independent Parliamentary Standards Authority (Ipsa), set up in the wake of the 2009 expenses scandal.

Mr Jones has asked Ipsa 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. It is right that these allegations are fully investigated."

The Herald:

Reforms introduced in 2010 mean MPs can no longer claim mortgage interest when they work in Westminster during the week.

Since then dozens of MPs, including Mr MacNeil, say they have had to rent out their London homes and stay in hotels to avoid subsidising their jobs.

Mr Grayling’s comments came after the SNP's Commons leader Pete Wishart attacked the Tory party for its conduct during the EU referendum.

He told MPs: "The debate in the Tory Party is hardly reaching Churchillian standards of discourse.

Read more: Stewart Hosie's independence role questioned following love triangle revelation

"Apparently it's all about insults, personal attacks and tabloid smears, according to (Steve Baker, Tory MP for Wycombe) this morning on the radio."

Mr Grayling replied: "I'm really not sure this is the week for the Scottish National Party to be talking about stories in the tabloids.

"I've read the news, there has to be something in the water in Scotland.

"Mr Speaker, as you'll remember me telling the House a few months ago the honourable member for the Western Isles (Mr MacNeil) wrote to me about recess dates because he wanted to put the ram in with the ewes.

"At that time I thought he was talking about sheep."

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."