Leading Green party members within the Richmond Park constituency have condemned Caroline Lucas’s decision to back the Liberal Democrat candidate against Zac Goldsmith in the byelection this week and called on their members to vote for Labour’s Christian Wolmar instead.

Clare Keogh, who stood for the neighbouring Kingston and Surbiton constituency in 2015, and Ryan Coley, the party coordinator for the Kingston Greens, were among those who signed a letter to the Guardian urging Green voters in Richmond Park to reject the Lib Dems because of their “regressive role with the Tories in government”.

The Richmond Park byelection and prospects for a progressive alliance | Letters Read more

Members of the Green branches in Kingston, and in Richmond and Twickenham, voted not to contest the byelection, triggered by Goldsmith’s resignation from the Conservative party over the decision to expand Heathrow.

The Lib Dem candidate, Sarah Olney, is also an opponent of Heathrow expansion and the party has high hopes of beating Goldsmith on a pro-EU platform, given that Goldsmith backed Brexit in a constituency with one of the highest remain votes in the country. The Conservatives are not putting up a candidate and Ukip has backed Goldsmith.

Lucas visited Richmond Park over the weekend to campaign with Olney. “This is no normal byelection,” she said. “The local Green party has stepped up at this unique moment and is backing Sarah Olney as the best hope of beating Zac Goldsmith and denting the government’s plans for a painful Brexit from the European Union.”

Kieron Merrett, a Kingston Green party member who sits on the national executive committee, said the branch had been taken aback by Lucas’s comments. “We reject Caroline Lucas’s endorsement of the Liberal Democrat candidate and encourage local Greens to support the Labour party candidate,” he said.

In their letter, local Greens said they supported the concept of a progressive alliance, but simply endorsing another candidate was not the answer, citing the Lib Dems’ record in coalition with the Conservatives, including the bedroom tax and university tuition fees increase, as well as launching the Airports Commission in 2012, an independent review that eventually supported expanding Heathrow.

“Unfortunately, we have no progressive alliance and no Green party candidate in Richmond Park,” the letter said. “Therefore, although not our first choice, we will be supporting Christian Wolmar, the Labour party candidate, as the best option available. We encourage other local Green supporters to do the same.

“But we note that, just like Caroline’s support for the Liberal Democrat candidate, this is neither a progressive alliance, nor is it the Green party’s democratically approved policy.”

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A spokesperson for Lucas said: “The best chance of beating the regressive alliance around Zac Goldsmith is backing Sarah Olney in this election. Nobody could claim that the recent history of either the Lib Dems or Labour is perfect – indeed, on issues such as tuition fees and NHS privatisation, the [Conservative-Lib Dem] coalition simply built on the Labour party’s foundations – but an alliance requires compromise and to constantly keep an eye on the bigger picture.

“No one ever said that the new kind of politics would be easy for everyone involved, but hurdles have to be overcome to have the best chance of beating the Tories. The vast majority of people in the local Green parties involved voted to not field a candidate, but some individuals in Kingston Green party never agreed with that decision, a completely legitimate position to take.”

Goldsmith remains favourite to win as an independent, but lines have been blurred throughout the byelection, which takes place on Thursday. The former FA chairman and BBC director general Greg Dyke, who lives in the constituency, has also declared his support for Olney, despite being a former Labour party member.

“We are living in uncharted times, shown by the fact that there is no Conservative candidate in this byelection,” he wrote in a letter to the Guardian. “This is the moment for the people of Richmond Park to forget their normal voting preferences and make it very clear to the government that they still oppose Brexit.”