The JC understands that Greenstein attended a pre-conference workshop organised by Greens for Palestine about the antizionist motion due to be debated this weekend.
His attendance at the online meeting has fuelled fears that the party is becoming a magnet for those expelled from Labour during the height of its antisemitism crisis.
BOURNEMOUTH, ENGLAND - OCTOBER 05: Green Party leader Zack Polanski is interviewed by a member of the media on the final day of the Green Party Conference, at Bournemouth International Centre on October 05, 2025 in Bournemouth, England. The Green Party go into this year's conference with new leader Zack Polanski and will focus on the cost-of-living, climate crises and the NHS. (Photo by Finnbarr Webster/Getty Images)Getty Images
In an interview in The House magazine earlier this month, Polanski – who grew up in a Zionist household and said in 2018 that, as a Jew, he could not vote for Corbyn – appeared to backtrack on his view of the former Labour leader.
The Labour Party was found to be in breach of the Equality Act during the crisis, but Polanski claimed there had been a “cynical and systemic deliberate obfuscation of a really serious issue like antisemitism”.
Adding that that he had read Paul Holden’s book, The Fraud, the Green leader cited the “political weaponisation” of Jew-hate.
Long-time Green Party member, former councillor and founding member of the Jewish Greens group, Elise Benjamin, has warned that an influx of former Labour members risks reshaping the party.
“Jewish Greens were keeping an eye on the fallout in Labour from Corbyn. We got about three people joining after that, and we were quite relieved. But now [former Labour members] are joining in swathes,” she claimed.
The JC understands there is no systemic process for vetting new Green members.
Activists supporting this weekend’s motion, which defines “Zionism as racism” have been pushing for supporters of the motion to join the party to vote.
An emergency motion was launched in coordination with the Jewish Greens group in opposition to the antizionist motion.
But now Jewish Voice for Liberation (JVL), the far-left campaign group formerly known as Jewish Voice for Labour is urging its supporters to join the Jewish Greens in order to reshape its direction.
In a message to members, JVL said: “Jewish Greens are at present controlled by a group of ‘Liberal’ Zionists.”
“If you are a Jewish member of the Greens please consider joining them so we can move the group in the progressive antizionist direction.”
The Jewish Labour Movement (JLM), which contested antisemitism in Corbyn’s Labour, has written to Polanski to warn him that if the party adopts the motion, it would be opening the door to unchecked Jew-hate.
In a letter sent to the Greens leader on Thursday, ahead of the Spring Conference, JLM raised the referral of Labour to the Equality and Human Rights Commission (EHRC) and the finding that the party was guilty of unlawful indirect abuse of Jewish members.
JLM chair Ella Rose-Jacobs and secretary Rebecca Filer suggested that if passed, the antizionism motion “would mean the Green Party would ‘reject the adoption or use’ of the International Holocaust Remembrance Alliance definition of antisemitism, as well as ‘alike’ definitions.”
“Without clear definitions that are used across civil society and British institutions on antisemitism, it leaves the Green Party as a potential space for antisemitism to go unchecked, and ultimately would lead to Jewish people being isolated and experience discrimination within your party,” the letter warned.
“JLM knows where the route the Green Party is taking will go, and we would like to relay our experiences to you… Parties on the left are not immune to antisemitism, both historically and today,” they wrote.
The warning about the contentious vote comes as one senior member has quit the Greens over its radical shift to the left.
Norfolk councillor, Michael de Whalley, left the party this week, citing its shift towards a “left-wing populist stance”.
Gorton and Denton by-election winner Hannah Spencer, of the Greens, takes a selfie with party leader Zack Polanski (Photo: Getty)AFP via Getty Images
Former co-leader Adrian Ramsay said he was “deeply sorry” about Whalley’s departure, describing him as a “deeply committed long-term Green”.
“As a party we must adopt a strategy which unites long-term members & new supporters behind our core values,” Ramsay said.
Under Polanski’s leadership, the Greens have surged in the polls, with membership reported to have tripled to more than 200,000, and a by-election win in Gorton and Denton last month, which saw the party campaign on Gaza.
A Green Party Spokesperson said: "The Green Party is open to anyone who shares our values and wants to be part of our movement working for social and environmental justice. Many people move to The Greens from other political backgrounds and are warmly welcomed. If they want to go on to represent us in elections, or if any concerning past behaviour is flagged with us we will vet them. We have robust internal processes designed to respond to any behaviour not in line with Green values."
The spokesperson added, "We don't comment on individual members".
Greenstein told the JC: “I am pleased that the Green Party is waking up to the fact that the Israeli State poses an existential threat to humanity, as witnessed with its current war on Iran. I welcome the proposed motion that Zionism is a form of racism.
“Nearly seven years ago you reported in shocked tones that fact that I had said that the Israeli state was ‘Hitler's bastard offspring’.
"Can anyone doubt today with the genocide in Gaza, the deliberate targeting of children and statements by MKs such as Yitzhak Kroizer that there are no innocent Palestinian civilians or children, an exact mirror of what Himmler and others said about Jews, that my analysis has been proven correct?”
He added: “The reason why lots of victims of the false allegations of antisemitism in the Labour Party have joined the Green Party is because the allegations were false.”
He did not respond directly to the allegation that he is a “notorious antisemite”.
