The Green Party has stood down its candidate to help Labour try to unseat former Tory leader Iain Duncan Smith.
Mr Duncan Smith has been MP for Chingford and Woodford Green since 1997, and has a majority of 2,348.
The Green Party, Liberal Democrats and Plaid Cymru formed an electoral pact earlier this month. Supporting Labour in Chingford does not form part of that pact, the Greens said.
The Conservatives have been contacted for comment.
In a statement the local Green Party said the decision for John Tyne not to contest the election was made with the “ultimate hope of favouring the campaign of the Labour candidate” Faiza Shaheen.
A Green Party spokesperson it “was a decision taken by the local party”.
However, they added: “If Labour were serious in their concern for the environment they should reconsider their isolationist position on arrangements.”
Ms Shaheen, head of the Centre for Labour and Social Studies, said she was “so grateful” for the decision.
She said: “I will continue to fight hard for climate policy and democratic reform.”
The Liberal Democrats have selected Dr Geoffrey Seeff as their prospective parliamentary candidate for the constituency.
Mr Duncan Smith has been MP for the area since 1992, representing Chingford until 1997 when the boundaries were re-drawn to include Woodford Green.
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