GREEN leader Zack Polanski said today’s Gorton and Denton by-election result will “transform the face of British politics” as Labour MPs, union and campaign groups called for Sir Keir Starmer to resign.

His party’s winning candidate Hannah Spencer slammed a broken Britain where workers were “bled dry” to “line the pockets of billionaires,” after triumphing with as 12-point lead over nearest rivals Reform and knocking Labour into third place.

“Working hard used to get you something,” she said in her victory speech.

“It got you a house, a nice life, holidays. But now, working hard, what does that get you?

“People work hard but can’t put food on the table, can’t get their kids school uniforms, can’t put their heating on, can’t live off the pension they worked hard to save for, can’t even begin to dream about ever having a holiday, ever.”

The embattled prime minister admitted coming third in the Greater Manchester seat Labour has held since 1931 was “very disappointing” but vowed to “keep on fighting.”

He attempted to smear the Greens as “extremists” while his predecessor and Your Party parliamentary leader Jeremy Corbyn MP welcomed the 34-year-old plumber’s sensational victory over the far-right Reform UK.

The Communist Party said the result “puts the lie to the political spin that working-class voters fall for the far right, racist dogwhistle politics of Reform, or the lesser of two evils choice presented by Keir Starmer’s Labour Party,” adding it was a verdict on the latter’s “corrupt, broken politics.”

Labour-affiliated transport union TSSA general secretary Maryam Eslamdoust led the calls for Sir Keir’s immediate resignation after Ms Spencer emerged victorious for the Greens in Thursday’s by-election with 14,980 votes — a majority of 4,402.

Labour’s vote-share almost halved from 2024 to 25.4 per cent in the by-election while second-place Reform more than doubled its share to 28.7 per cent.

At a rally in Manchester, Mr Polanski said the result was “an existential crisis for the Labour Party” as Sir Keir’s socialist predecessor Mr Corbyn vowed to work constructively with the Greens as he was “proud to support a campaign built on hope and humanity.”

Unions demanded a change of course from Sir Keir ahead of crucial elections in May, with warnings his days in No 10 could be numbered.

Scottish Labour MP Brian Leishman called for the PM to stand down as blame for the disastrous result “lies with Starmer and the people that surround him.”

He slammed Starmerite members on Labour’s national executive committee for blocking Sir Keir’s leadership rival, Greater Manchester mayor Andy Burnham, from standing in the seat as “wrong and [Starmer] did it for his own benefit.”

And former Labour chair Ian Lavery lamented an “entirely predictable disaster [that] lies squarely at the feet of those who never tire of telling us they have ‘changed the party’.

“Many are talking about an existential threat to the Labour Party itself. This election should prompt a serious reckoning for the man at the top, but there is nothing so far that suggests he or his aides are listening.”

Labour MP Karl Turner described the by-election result as “catastrophic” for his party.

In an interview on the Today programme, he agreed with the Unison leader Andrea Egan that Labour needing to move to the left, saying: “The reality is we can’t possibly out-rightwing Reform on immigration and we can’t out-leftwing the Greens on progressive policy.”

Secretary of the Socialist Campaign Group of MPs Richard Burgon blamed “Starmer and his clique” for Labour’s defeat.

“They put factional interests over having the candidate best placed to win, Andy Burnham,” he added.

“If Labour is to be the ‘Stop Reform’ party, then the leadership must stop treating progressive voters with contempt — and start appealing to them.”

Labour MP for Norwich South Clive Lewis described the defeat as “a punch in the face” for Sir Keir’s premiership but warned changing the leader “without changing the politics would be a waste of time.”

Left Labour MP Jon Trickett told Times Radio the result “signals a bigger change in the way that people see the country, its politics and its leaders, and Labour absolutely must reflect on this in a serious way. 

“And that does mean, I’m afraid, that the prime minister needs to reflect on his own position.”

A spokeswoman for Momentum said: “What we need to see is a fundamental change of direction and policy. 

“No one can plausibly see that change happening under Keir Starmer.”