Nigel Farage says party is endorsing former Tory MP, who resigned over Heathrow expansion, instead of fielding a candidate

Ukip has endorsed Zac Goldsmith, the former Conservative MP who is now standing as an independent in the Richmond Park byelection, which will take place on 1 December.

The party’s interim leader, Nigel Farage, said Ukip would not put up a candidate against Goldsmith, who backed leave in the EU referendum, and its supporters should vote for him to stop the pro-EU Liberal Democrats from winning the seat.

Goldsmith, who was the Conservative candidate for mayor of London in May’s election, resigned as an MP earlier this week after the government’s decision to approve expansion at Heathrow, which he opposes. The Conservatives have said they will not put up their own candidate against Goldsmith.

The Lib Dems, who held the west London seat until 2010, have high hopes of winning it back, thanks to their opposition to Heathrow expansion and their support for the EU. A large majority of voters in Richmond Park voted to remain on 23 June.

Ukip, which came fifth in the seat at last year’s general election, said it respected Goldsmith’s decision to fight Heathrow expansion.

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“Zac Goldsmith has resigned on a matter of principle and Ukip admire him for having the courage to do so,” a spokesman said. “Ukip have always believed that Gatwick was a preferred option to Heathrow.

“Recognising Zac as a principled man, who was fully committed to helping get Britain out of the European Union, Ukip leader Nigel Farage, in conjunction with our national executive committee, have agreed that we will not be fielding a candidate in the upcoming byelection for Richmond Park.”

The spokesman said the Lib Dems were “committed to overturning the result of the 2016 referendum and ignoring the will of the British people. This must not be allowed to happen.”

The Lib Dem leader, Tim Farron, said the endorsement showed Goldsmith was “the Ukip candidate”.

“Goldsmith claimed Brexit has nothing to do with this byelection,” he said. “The very public endorsement he has picked up from the party of Nigel Farage nails that lie.

“This byelection presents a golden opportunity to defeat one of the leading Brexiteers, who is determined even [to] take Britain out of the single market. He might be able to afford the huge damage this would do to our economy, but many people in Richmond Park are worried about the effect on their jobs and livelihoods as a result of the Conservative government playing Russian roulette with the British economy.

“Zac Goldsmith can get as many hard-right candidates to give him a clear run as he likes; he knows he faces a major battle with a Liberal Democrat party determined to keep Britain open, tolerant and united.”

On Wednesday, the Labour frontbenchers Clive Lewis and Jonathan Reynolds, as well as the former shadow minister Lisa Nandy, suggested their party should not contest the seat, where Labour came third in 2015. The trio said it would be preferable not to split the progressive vote, with the Lib Dems standing a chance of reducing Theresa May’s Commons majority.

However, Labour’s NEC has decided it will contest the seat. Senior party figures, including the deputy leader, Tom Watson, were angered at the suggestion that the party would not field a candidate in the byelection.

The local Green party has also decided to contest the seat, according to the website Bright Green, although it said it was open to talks with the Lib Dems about cooperation.

A Green party spokesman said there was “a real chance to reduce the Conservative majority in parliament and replace a candidate disgraced by his racist campaign to be mayor of London”.