A Conservative MP embroiled in a scandal has announced he will stand down – triggering a by-election in his Somerton and Frome constituency, Sky News understands.

David Warburton was suspended from the party in April 2022 pending the outcome of an Independent Complaints and Grievance Scheme (ICGS) investigation into allegations of harassment and drug abuse.

Speaking to the Mail On Sunday, the 57-year-old said he will resign his seat this weekend because he was denied a fair hearing by a parliamentary harassment watchdog investigating allegations that he had made unwanted advances towards two women.

He admitted to the newspaper that he had taken cocaine after drinking “incredibly potent” Japanese whisky with a third woman.

The woman secretly photographed and recorded him after he visited her flat following a late-night vote in the House of Commons.

Mr Warburton has now accused the parliamentary authorities of being “terrified” of the MeToo movement saying he “didn’t stand a chance” from the outset after the ICGS investigation was launched.

In his resignation letter he reportedly says the “malicious allegations” and “flawed” 14-month investigation “has inflicted unimaginable and intolerable destruction on my family and on me”.

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Mr Warburton was first elected in 2015 with a majority of 20,268, or 53% of the vote. According to the MP’s website, at 18.3%, this represented the largest constituency swing to the Conservative Party.

He was re-elected in 2017 and 2019, with majorities of 22,906 and 19,213, respectively.

Following Mr Warburton’s announcement of his decision to step down, a Conservative Party spokesperson said: “The IGCS is an independent body set up by parliament and the Conservative Party respects its processes. Mr Warburton had the whip withdrawn over these complaints last April and has not sat in parliament as a Conservative since.”

Mr Warburton’s departure means Prime Minister Rishi Sunak and his party are facing another by-election after Boris Johnson and two of his allies, Nadine Dorries and Nigel Adams, announced they will resign just over a week ago.