The Green Party has comprehensively won the Gorton and Denton by-election in a stunning result which saw Labour slump to third place.

In a crushing blow for Keir Starmer, the Greens’ Hannah Spencer came first with 14,980 votes following a bitterly-fought contest.

Reform UK’s Matt Goodwin came second with 10,578, despite his party’s lead in the national opinion polls, ahead of Labour’s Angeliki Stogia on 9,364.

Polling guru Sir John Curtice said it was “the worst possible result for the prime minister”.

It is the first time the Greens have ever won a Westminster by-election and means the party now has five MPs.

The by-election was called following the resignation of former government minister Andrew Gwynne on health grounds.

He won the newly-created seat for Labour at the 2024 general election by more than 13,400 votes.

Labour’s terrible performance will pile further pressure on Keir Starmer, who campaigned in the seat earlier this week and who has endured a torrid time since becoming prime minister barely 18 months ago.

In particular, the prime minister’s decision to block Manchester mayor Andy Burnham from standing as the Labour candidate will undoubtedly come in for intense criticism.

Lucy Powell, Labour’s deputy leader, all-but conceded defeat shortly before 3am.

She told Sky News: “What’s clear is that the Greens turned out their vote higher than they might otherwise expect to have done.

“I want to win elections, that’s what I’m in politics to do, and I wanted Angeliki Stogia to be my colleague in parliament, I think she would have been a fantastic MP.

“But what I think is really clear is that there is a big majority in this constituency that hasn’t voted for Reform, and on the day the Greens have managed to win that argument they were best placed to do that.”

Labour chair Anna Turley said: “This result is clearly disappointing. By-elections are normally difficult for the party of government, and this election was no different.”