Labour has suffered a historic defeat at a crucial by-election in a seat that has been red since it was created in 1982.

Trudy Harrison, the Conservative candidate, defeated Labour’s Gillian Troughton, a volunteer for St John Ambulance, by 2,147 votes.

The Cumbrian seat of Copeland – and its predecessor seat Whitehaven – has been represented by Labour since 1935.

The Conservative victory also marks the first time a rival party has been defeated by the party of government at a by-election in 35 years, when, in 1982, the Labour MP for Mitcham & Morden defected from the party to the SDP.

The constituency is heavily dependent economically on the Sellafield nuclear processing facility and Labour leader Jeremy Corbyn’s past opposition to nuclear power has not gone down well.

Labour sought to counter with a hard-hitting campaign focusing on possible cuts to maternity services at the West Cumberland Hospital, with a claim local midwives believed it would lead to “mothers and babies dying”.

In a sign of how confident the Conservatives were in the scenic constituency on the Cumbrian coast, Theresa May, the Prime Minister, visited the region just over a week ago to meet Ms Harrison.

The contest came after Jamie Reed, a persistent critic of the Labour leadership, stood down from his seat before Christmas triggering a three-way battle for his marginal northern seat. At the 2015 general election, Mr Reed secured 42 per cent of the vote compared to 35 per cent for the Conservatives.

As the results were counted in the early hours of Friday morning, senior Labour sources appeared to be conceding defeat, adding it was “neck and neck” and that “rural constituencies still to come in likely to favour Tories”.

On Thursday evening Mr Corbyn thanked those who campaigned for the party in the final hours and braved Storm Doris, which lashed parts of Britain with up to 94mph gusts.

He added: “The political establishment has let down Copeland and Stoke, who have seen their industries gutted, living standards stagnate and hope for a better future for their children and grandchildren decline.