The Greens have been branded “a racist party” after its members passed a motion declaring that “Zionism is racism”.
Activists at the party’s annual conference voted overwhelmingly by 1,022 to 813 to back it.
An amendment stating that Green Party members would not be targeted for attending Zionist synagogues was also defeated.
Party leader Zack Polanski was also criticised after he dodged the votes in order to campaign in Holborn and St Pancras ahead of Thursday’s crunch by-election.
Zionism is the belief that Jewish people should have their own state, although the precise definition has long been open to debate.
Critics of the motion said it risked sending out a message that Jews are not welcome in the Greens.
The issue has exposed deep splits in the party, with former co-leaders Adrian Ramsay and Carla Denyer issuing statements saying they were voting against the motion.
Reacting to the result, Rabbi Charley Baginsky and Rabbi Josh Levy, co-leads of The Movement for Progressive Judaism, said: “The motion is anti-semitic in its formulation and intention. By adopting it, the Green Party has made anti-semitism party policy and become a racist party.
“Jewish self-determination is a right. Declaring it racist is an attack on Jews.
“The Green Party has chosen to brand Jews who hold this belief as racists and make their equal participation in the party conditional on renouncing it.”
They added: “A party that votes against protecting Jews while debating whether their self-determination is racist is practising the racism it claims to oppose.”
Tory shadow home secretary Chris Philp said: “British Jews should not have to disclaim a belief in Jewish self-determination and the existence of Israel in order to be accepted by a British political party.
“One look beneath the surface of Zack Polanski’s Green Party shows a party toxic to its core. It is clear the Green Party cannot bring itself to stand unambiguously against those who hate Jews.”
Former Lib Dem leader Tim Farron posted on X: “That the anti-semitic entryists who have captured the Green Party are being antisemitic is no surprise.
“That the party leader skipped this vote and failed to use his authority to argue against them is an astonishing act of weakness. Real Greens are welcome in the Lib Dems.”
A Green Party spokesperson said: “This has been a serious and deeply felt debate within our membership. Our members value the ability to bring forward and decide party policy, and conference has now made its decision.
“The Green Party is an anti-racist party and has consistently opposed the illegal occupation of both Palestinian and Syrian land, called for an end to arms sales to the Israeli government and spoken out fearlessly about the devastating situation in Gaza and the West Bank.
“Those positions remain central to our approach. So too does our deeply held commitment to equality, justice and human rights for all and opposition to racism in all its forms.”
In an unusual move, Polanski, his two co-deputies and the Greens’ fives MPs issued a joint-statement saying they “will never tolerate any form of discrimination or harassment”.
The statement said: “We will continue to stand in opposition to genocide, ethnic cleansing, apartheid and the illegal occupation.
“We will continue to call out the heinous crimes of the Netanyahu government.
“And we will continue to work to ensure that the Green Party is an anti-racist party in every way.
“We know there is no conflict between supporting the rights of Palestinians and the rights of Jewish people.”
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