However, the complaints have been upheld under the new Independent Complaints and Grievance Scheme, The Sunday Times reported, with the politicians asked to respond.

The Scottish Lib Dems called for the party whip to be removed from both MPs, which would mean they would be forced to sit as independents and would be unable to stand for the party again if it was not restored.

A spokesman said: “The SNP have been vocal about misconduct on the Conservative benches, they should recognise that the same standards they demand of others ought to apply to them.”

‘Engulfed in sleaze’

Meanwhile, the Scottish Tories claimed that despite the partygate scandal, it was the SNP that was “engulfed in sleaze”.

“It appears that Nicola Sturgeon’s party has yet again failed victims of alleged sexual misconduct,” Stephen Kerr, the party’s chief whip, said.

“The SNP have shown a complete lack of transparency and have tried to brush these horrendous incidents under the carpet in the hope people will forget about them. The victims deserve better than to be treated as an afterthought by the SNP.”

Ms Sturgeon has previously admitted she was aware of a “concern” about Mr Grady but the party did not take formal action as a result.

He stepped down as chief whip in March last year, after a formal complaint was made and the allegations against him became public.

He was a senior party official before he was elected as MP for Glasgow North in 2015. He has not addressed the allegations publicly.

The result of the Westminster authorities’ investigation has been referred to an independent expert panel, which can recommend sanctions including suspension or expulsion from the House.

The SNP will also have to decide whether to take its own action against the MPs.

Mr Grady and Ms Gibson are yet to comment. 

An SNP spokesman said: “It would not be legally appropriate to comment while the independent parliamentary process is ongoing.”