Rishi Sunak could suffer the worst by-election drubbing in more than 50 years this week, one of his Scottish MPs has admitted.

Nuclear energy minister Andrew Bowie said it was possible the Tories could lose all three of the seats the party will be defending on Thursday.

It came just a day after the Prime Minister euphemistically said the contests would be “difficult” for the government.

On Sunday, former Tory health minister Steve Brine said a triple defeat would be a symptom of the party suffering from “long Boris” and the turmoil of the past year at Westminster. 

Many Tory MPs are wondering if the condition will last to the next general election, with the bookies expecting a Labour victory. 

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Labour is targeting two of the three by-election seats - Uxbridge & South Ruislip near London, where Boris Johnson was the MP until he quit amid scandal over Covid rule-breaking in No10, and Selby & Ainsty in Yorkshire, where the former PM’s ally Nigel Adams quit after being denied a peerage.

The Liberal Democrats, meanwhile, are focused on Somerton & Frome in their former South West heartlands, where David Warburton quit following an admission of cocaine use.

Mr Bowie, the MP for West Aberdeenshire & Kincardine, told Times Radio that a triple loss for the Tories was possible, the first time a government had suffered such a defeat in one day since Labour under Harold Wilson in 1968.

“Of course it’s possible we could lose all three – but it’s also possible that we might win all three,” he told Times Radio.

“I’m an optimist, I’m a Scottish Conservative and Scotland football fan – I have to be an optimist.”

Defeats in three diverse seats, two with Tory majorities of around 20,000, would pile pressure on Mr Sunak to revive Tory fortunes ahead of the party’s October conference.

The PM had been expected to reshuffle his cabinet in the autumn – Defence Secretary Ben Wallace has said he is standing down – but The Sun reported it could be much sooner. 

Downing Street said there were no plans for a shake-up this week.

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Campaigning in Somerton & Frome, LibDem leader Sir Ed Davey said voters there could “send Rishi Sunak and the Conservative Party a message on Thursday”.

He said: “Enough is enough, the Conservative party soap opera must end. The Conservative Party is simply not fit to govern this country.”