The would-be Richmond Park Green party candidate has said the decision to stand aside may have been the decisive factor in ensuring a Liberal Democrat victory last week.

Andree Frieze was the party’s chosen candidate before the decision was made to step aside in the election, clearing the path to victory over Zac Goldsmith.

She said she was still glad both local Green parties – Richmond and Twickenham and Kingston – did not contest the election.

It was revealed yesterday three members of the Kingston Green party complained they were pressured into standing aside in the byelection, partly due to a potential £250,000 donation to the party.

The money was not accepted, according to the report, after it failed to pass donation scrutiny.

Ms Frieze said: “We managed to change the election. It made it less about Heathrow, and it got people united behind one candidate.

“We feel if we had not stepped aside Zac Goldsmith would have won.

“We leafleted 25,000 households in the constituency to explain why we were not standing. We made a position out of not standing.”

A confidential report leaked yesterday, co-authored by Ryan Coley, the chairman of the Kingston Greens, and members Clare Keogh and Kieron Merrett, claimed the national party put pressure on the local group to stand aside.

It read: “Party staff added pressure on a small group of KGP (Kingston Green Party) members by telling us that there was an offer of a large donation to the party which was conditional on the party demonstrating its desire for a ‘progressive alliance’.

“KGP members were told this could affect the jobs of party. There was therefore a desire for local members to comply.

“Party staff present at the meeting on November 2 informed a group of KGP activists, in confidence, that the party staff were keen for us to agree to stand down.”

The Green party said it disputes many of the claims made, insisting it has not accepted major donations connected with the Richmond Park byelection.

A party source however did confirm a staff member discussed a potential donation with local members, and that this was an “error”.

Ms Frieze said the Richmond and Twickenham Greens would continue to work with the Kingston Greens.

She added that the Kingston group has “its own issues to resolve”.

The Conservatives, Mr Goldsmith’s former party, nor UKIP which announced its backing for Mr Goldsmith, stood candidates either.