The Greens will pull their punches in the Makerfield by-election campaign to give Labour a better shot at winning, the party's leader in Westminster has admitted.

Zack Polanski's party will not throw 'the kitchen sink' at the upcoming by-election, Ellie Chowns said on Monday – in a seeming stitch-up on the Left.

Speaking at the Hay Festival, Dr Chowns said: 'In this particular constituency, there is a question, I think, about the extent to which any party might throw the kitchen sink at a campaign.

'We threw the kitchen sink at Gorton and Denton, and we won it. Makerfield is a different kettle of fish.'

The Greens are currently set to stand a candidate in Makerfield, despite polling suggesting they would come in fifth place behind the Liberal Democrats, Restore Britain, Reform and Labour.

But senior party figures, activists and members have urged Mr Polanski to strike a deal with Mr Burnham – whereby the Greens step aside in Makerfield on the condition the latter commits to bringing forward proportional representation should he win and go on to topple Keir Starmer as PM.

But Dr Chowns on Monday ruled out such a deal, saying: 'We are a political party, we exist to stand in every election.'

And in a swipe at the Greater Manchester Mayor, she added: 'If Andy Burnham thinks he can't win against Reform unless everybody else steps out of the election, then that's not exactly the messiah that the Labour Party perhaps feels it needs.'

But the Greens deciding to run a light-touch by-election campaign will inevitably funnel votes towards Mr Burnham, who is hoping to oust Sir Keir and move Labour to the left.

And the Greens' game play in Makerfield is now piling more pressure on the Right to unite to keep Mr Burnham from No. 10.

Commenting on the Green Party's plans, former Conservative Cabinet minister Sir Jacob Rees-Mogg said: 'I fear the left is more politically astute than the right. At the last election they clearly had an informal cooperation over seats and now they admit it for the Makerfield by-election.

'The right must learn from this and work together in a similar fashion. As Margaret Thatcher said 'Marxists get up early in the morning to further their cause. We must get up even earlier to defend our freedom.' Unfortunately, we are now lie-a-beds.'

But a Reform UK spokesman said that the Makerfield by-election is 'a straight fight between Reform UK and Labour' and that 'no other party is in this race'.

'The only way to stop Open Borders Burnham from getting the keys to Number 10 is by voting for Reform UK,' they added.

A Green Party spokesperson said: 'We are looking forward to the campaign. We've demonstrated from our campaigning and wins in Gorton and Denton and the recent local elections that we can beat Reform.

'We're a democratic party and our local members are set to choose a candidate this evening.'