RISHI Sunak is faced with the yet another potentially damaging by-election after a former Tory MP resigned with immediate effect following accusations of sexual harassment and cocaine use.

David Warburton has stood down from his seat of Somerton and Frome, hitting out in an exit statement at an “extraordinarily difficult” 14 months fighting “malicious allegations”.

He claimed he had been denied a fair hearing by the Independent Complaints and Grievance Scheme (ICGS) and prevented from “speaking out” while it probed the accusations.

In his resignation letter he said had been left with “no choice” but to provoke “the upheaval of a by-election”, adding: “It is my hope that, in so doing, I can freely illuminate the methods of an oversight system not fit for purpose, so that friends and colleagues in the House can see the perverted process by which their own judgement may at any time be freighted.”

In an interview with the Mail on Sunday, Warburton admitted to taking cocaine after drinking “tons of incredibly potent” Japanese whiskey, but denied claims that he harassed a female political aide in his Westminster flat.

The resignation will trigger an electoral battle in his Somerset constituency, adding to the by-elections already due to take place in Boris Johnson and Nigel Adams’s constituencies.

Johnson loyalist Nadine Dorries has also announced that she will quit as an MP although has yet to formally trigger a by-election.

Earlier this week she stated that she was seeking clarification of why she was denied a seat in the House of Lords before officially stepping down.

Warburton took the seat from the Liberal Democrats in 2015 and has a 19,213 majority but the party is already stepping up manoeuvres to reclaim it.

Liberal Democrat deputy leader Daisy Cooper said: “Time after time the Conservatives have mired themselves in sleaze and scandal neglecting the issues that really matter to people. Then they decided it was okay to leave local people in this seat without any proper representation at all.

“This by-election will be a clear contest between the Conservatives and the Liberal Democrats, Labour finished third last time and are completely out of the race. The people of Somerton and Frome need a local champion and they can have that at the next election by choosing our local Liberal Democrat candidate Sarah Dyke.”

Meanwhile Labour’s national campaign co-ordinator Shabana Mahmood accused the Prime Minister of being “too weak to act himself”.

“Yet again, we see a Tory MP resigning in disgrace, after Rishi Sunak was too weak to act himself. Enough is enough,” she said.

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“Britain can’t afford this weak Conservative prime minister with a party too divided to govern as families struggle with the cost of living. It’s time to turn the page on 13 years of Tory chaos. We need a general election now and a Labour government led by Keir Starmer.”

Warburton had been sitting in the Commons as an independent after having the Tory whip suspended last April over the allegations.