The Green party's conference in Brighton voted 1,022 to 813 on Sunday to adopt a binding policy treating Zionism as a form of racism and calling for a single Palestinian state in place of Israel. The motion passed despite opposition from four of the party's five MPs, immediately triggering a cascade of political consequences that extend well beyond the policy's substance. Labour moved fast. Party chair Bridget Phillipson called the vote "shameful," and senior figures lined up to declare future cooperation with the Greens effectively dead. One minister said they could not foresee how the two parties could work together; a government official said Labour should formally rule out any coalition or arrangement. A source linked to the Jewish Labour Movement argued Labour should "absolutely" refuse to govern with the Greens, suggesting the policy could breach equality law in its treatment of Jewish members. The timing is not accidental. Thursday brings the Holborn and St Pancras byelection — Keir Starmer's former seat — where Green candidate Zack Polanski has poured enormous resources into what he calls a "knife-edge" contest. Labour views the Zionism motion as a gift: a way to simplify the political argument against a party that has increasingly targeted disillusioned Labour voters on the left. The Greens' massively increased membership has fuelled their campaigning efforts, but Labour remains the favourite. Polanski, who left the conference early to campaign, has attempted a straddle — neither endorsing nor criticising the motion, saying antisemitism and criticism of Israel "are and must always be completely distinct" while remaining "proud of the party's stance on Palestinian rights." This careful positioning reflects the bind: the motion energises parts of the Green base while alienating potential coalition partners and mainstream voters. The fallout extends to the Liberal Democrats. In Southwark, where the Greens and Lib Dems govern together after May's local elections, the two parties issued a joint statement against antisemitism that conspicuously avoided mentioning the new Green policy. Senior Lib Dem peers were not mollified. Baroness Ludford called the statement "greenwash" and demanded the Lib Dems distance themselves entirely. Baroness Featherstone was blunter: "I would ditch them. Grow a pair!" The European Greens and German Greens have also distanced themselves from the policy. The deeper political dynamic is structural. Months of speculation about possible Green-Labour cooperation — Polanski himself floated an electoral pact under Burnham or Rayner — are now definitively over. Labour gains a clean differentiation tool against a left-flank competitor, while the Greens face isolation from every potential governing partner simultaneously. The policy may reflect genuine conviction among the 1,022 members who voted for it, but its political cost is being borne by the party's parliamentary wing and its coalition prospects. What matters now is whether the Greens' conference sovereignty — members binding a reluctant parliamentary party — becomes a recurring pattern that locks the party out of mainstream politics, or whether this is a high-water mark that forces internal reform. The byelection result on Thursday will be the first data point.
