The Green Party's debate over whether to oppose Andy Burnham at the Makerfield by-election has reignited calls to 'unite the Right' to stop a Left-wing coalition.

Zack Polanski's party will select a candidate on Wednesday but there is still an internal debate raging over how hard the Greens should campaign against the Manchester Mayor.

Senior Tories have called for their party to stand aside at the by-election next month to give Reform UK the best chance of halting the Left-wing Labour Mayor's return to Westminster.

Labour won Makerfield at the 2024 election with a majority of 5,399 over Reform, while the Tories came third with 4,379 votes - meaning the majority would be virtually wiped out if they stood aside.

But both parties have so far resisted calls for a pact. Reform on Tuesday announced local plumber Robert Kenyon as their candidate, while the Tories are expected to select theirs this week.

Former Green Party leader Caroline Lucas has led calls for Mr Polanski to 'put country before party' and not go all-out against Mr Burnham - a move that could help him see off the threat from Reform.

Meanwhile Mr Polanski has previously described the Mayor of Greater Manchester as somebody he could work with to stop Nigel Farage, reigniting fears of a Left-wing coalition at the next election.

Former Tory MP Lord Craig Mackinlay said he believes the Conservatives should stand a candidate in Makerfield as 'that is what political parties do', but he warned an agreement will have to be reached on the Right in future to stop a Left-wing 'rainbow alliance'.

He said: 'I have no doubt there will be deals done between Greens, Labour, perhaps even a bit of Lib Dem in there, Plaid Cymru, SNP, and whoever else.

'They will say "we won't do much here, nudge, nudge, wink, wink, you have a go at that one, you're the best ones to win this". I have absolutely no doubt that will happen amongst the Left.'

Lord Mackinlay called on the Tories and Reform to 'show each other a bit of leg' as he warned that a coalition between Labour and Mr Polanski's Greens poses a 'very dangerous risk' to the country.

He added: 'I think there will be a moment of realism, where the Right will go, hold on, what are we in this for? Are we in this for ourselves or are we in this for the country? And I hope that happens, I really do.'

However it is by no means certain that the Green Party will hold its fire against Mr Burnham as there are some senior figures who argue he cannot be trusted and that the Greens are 'looking to replace' Labour.

The decision on how hard to campaign will be made by the Green's executive committee. Mr Polanski is one of about two dozen members, but his view is likely to be crucial.

Several Tory MPs have already called for a pact with Mr Farage's party at the Makerfield by-election that is expected to take place on June 18. Such a move could negate any move by the Greens to give Mr Burnham their tacit backing.

Former business secretary Sir Jacob Rees-Mogg called for the Conservatives to make a quid pro quo pact with Reform to stand aside for each other at upcoming by-elections in Makerfield and Aberdeen South.

Sir Jacob urged both parties to put the 'interests of the country ahead of narrower party-political interests' in order to 'fend off the very Left-wing prospect that is in sight'.

However Tory leader Kemi Badenoch has insisted she has ruled out 'any deals' with Mr Farage, telling GB News: 'We will be standing a candidate at this election.'