Senior Greens have signed a joint statement urging Zack Polanski to consider giving Labour a clear run in the Makerfield by–election.Former party leaders and councillors warned the contest must be approached with 'trepidation' – as Andy Burnham's appointment could offer a 'unique opportunity' to reform the voting system.It follows calls to 'Unite The Right' and stop the Greater Manchester Mayor from returning to the Commons, paving the way for a Labour leadership contest.The first survey of the by–election last week showed the vote on a knife edge – putting Mr Burnham on 43 per cent and Nigel Farage's Reform UK candidate close behind on 40 per cent.The Green letter, signed by the likes of former party leader Jonathan Bartley and ex–councillor and author Rupert Read, states: 'Greens have always put their values and the climate and nature first. Which is why we approach the Makerfield by–election with some trepidation.'If Burnham will commit to backing proportional representation for the next general election Labour manifesto so that it is in place by the election after next, then on this unique occasion we don't think Greens should run a full campaign against him.' Senior Greens have signed a join statement saying Zack Polanski (pictured) should consider giving Labour a clear run in the Makerfield by–election (file image) The Green letter was signed by former party leader Jonathan Bartley (pictured) and ex–councillor and author Rupert Read (file image) The first poll of the contest put Labour on 43 per cent support, with Reform on 40 per cent as Andy Burnham (pictured) bids to return to the CommonsThe letter admits Makerfield is 'not a seat the Greens can win' – adding 'it will be a straight fight between Labour and Reform', The Sunday Times reports.A proportional representation voting system would allow for a closer reflection of smaller parties' votes in Parliament.Last week Mr Burnham said the current first–past–the–post system should change to enable 'less point–scoring, more problem–solving' and make politics 'more place first rather than party first'.The comments were welcomed by Mr Read who said he hoped the Greens would not 'move heaven and earth to stop [Burnham]' if he committed to electoral reform.Former Reform MP Rupert Lowe's party Restore Britain was predicted in last week's Survation survey to win 7 per cent of the vote – while the Conservatives were on 2 per cent.Meanwhile the Lib Dems have been placed at 4 per cent and the Greens at 3 per cent.Mr Farage said the findings exposed a 'two–horse race' in the Brexit–backing seat. 'Robert Kenyon is the only candidate who can stop Andy Burnham. This is a two–horse race – nobody else comes close,' he said.Join the discussionShould smaller parties step aside to help Labour win, or does this betray true democracy?What's your view? Nigel Farage said the contest was a 'two horse race'. Reform's candidate is Robert Kenyon, left