The Green Party candidate in Iain Duncan Smith’s constituency has stood aside with the aim of helping Labour unseat the former Conservative leader in next month’s election.

The move in Chingford and Woodford Green is the second occasion on which Greens have stood down candidates locally in Labour’s favour in Tory-held marginals, in what appear to be informal anti-Conservative initiatives not sanctioned by the party centrally.

It is certain to fuel demands for similar arrangements around the country, following the announcement by Brexit Party leader Nigel Farage that his party is standing aside in all 317 seats taken by Tories in the 2017 election.

Brexit figurehead Duncan Smith has held the north-east London seat since 1992, but his advantage over Labour in 2017 was a slim 2,438, with Greens taking 1,204 votes and Liberal Democrats 2,043, making him highly vulnerable to tactical voting.

The seat is being vigorously targeted by Labour, whose candidate, the economist and director of the Centre for Labour and Social Studies thinktank Faiza Shaheen, thanked Greens with a promise to “fight hard for climate policy and democratic reform”.

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The co-ordinator of the local Waltham Forest and Redbridge Green Party, Andrew Johns, said the party was “tactically withdrawing” its candidate “with the ultimate hope of favouring the campaign of the Labour candidate.

“While there are still some differences of opinion between the Greens and Labour on environmental targets, Faiza is an advocate of a more progressive politics and has agreed to work with local Green Party members in our fight against airport expansions and for ambitiously reducing carbon emissions,” he said.

The Green candidate selected for the Chingford seat, John Tyne, added: “The actions of IDS as the architect of the failed rollout of Universal Credit mean that we believe he is unfit for office.

“The party believes that its withdrawal from this election offers the best chance for voters to register a concerted vote against him and his failed policy.”

Chingford and Woodford Green was not on the list of 60 seats agreed by a Remain Alliance of Liberal Democrats and Greens, where the parties will stand down candidates in order to improve the chances of electing anti-Brexit MPs.

A Green Party spokesperson said: “This was a decision taken by the local party. The Green Party places local democracy and local parties at the heart of its operations and in this election we will be standing in the vast majority of seats across the country and more than in 2017.

“The first weeks of this campaign have shown how it is the Green Party who are putting the climate front and centre of this election. While Labour are still supporting airport expansion across the country, we are putting forward a transformative Green New Deal which will usher in the green transport revolution so clearly needed if we are to make the UK carbon neutral by 2030.

”If Labour were serious in their concern for the environment they should reconsider their isolationist position on arrangements.”