Former Liberal Democrat leader Sir Vince Cable is to step down as an MP at the next election, the party has announced.

The news will spark a scramble for Cable’s Twickenham seat, with newly-defected Lib Dem MPs Chuka Umunna and Sarah Wollaston thought likely to be at the head of a long list of would-be candidates.

Despite falling briefly into Conservative hands from 2015-17, the south-west London constituency is regarded as one of the Lib Dems’ safest seats, with Sir Vince taking more than 50 per cent of the vote at the last election.

Mr Umunna, who quit Labour in February to found The Independent Group only to defect again to the Lib Dems in June, is thought to be highly vulnerable to his former party in the Streatham seat which he has held since 2010.

A move to Twickenham, which has been Lib Dem since 1997 apart from the two-year period after the party’s electoral meltdown in 2015, would be seen as a way to find a more secure home for the party’s Treasury spokesman.

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Equally, Dr Wollaston is thought to have little hope of surviving an election in Totnes – an area which has returned Tory MPs since the 1920s – following her defection from the Conservatives to The Independent Group in February and her later move to the Lib Dems in August. The influential Commons Health Committee chair is thought likely to seek another seat before the poll, which must take place by June 2022 but could come as early as this autumn.

Sir Vince, 76, has served as MP for Twickenham since 1997, with a two-year break form 2015-17. He regained the seat in 2017 with a 9,762 majority and a 52.8 per cent share of the vote.

Vince Cable ended his leadership on a high with strong results in local and European elections (Getty)

He was the party’s deputy leader under Sir Menzies Campbell and Nick Clegg from 2006-10 and was business secretary in the coalition government from 2010-15, when he controversially oversaw the increase in university tuition fees and the sell-off of Royal Mail.

He was selected unopposed as party leader in 2017 after the resignation of Tim Farron, and served until July this year, handing over to Jo Swinson at a high point after the Lib Dems’ spectacular results in local and European elections.

A Lib Dem spokesperson said: “Vince has enjoyed a fantastic parliamentary career in the Liberal Democrats and representing the people of Twickenham.