British Prime Minister and leader of the Labour Party Andy Burnham has ruled out any future coalition agreement between his party and the Green Party while it maintains a policy declaring Zionism, the movement supporting Jewish national self-determination, to be a form of racism.

Speaking in the British parliament this week, Burnham condemned the policy adopted at the Green Party’s annual conference earlier this month, describing it as antisemitic.

“It is wrong, it is antisemitic, and this side of the House will have nothing to do with it,” Burnham said.

“We cannot support a partnership with a party that holds the position that has recently been adopted.”

The controversy follows a vote at the Green Party’s conference in Brighton in early October, when members supported a motion defining Zionism as a racist ideology and calling for the establishment of a single Palestinian state across the territory currently comprising Israel and the Palestinian territories.

The motion passed by 1 022 votes to 813, despite opposition from four of the party’s five MPs and several former leaders.

The vote represented a small fraction of the Green Party’s approximately 230 000 members, prompting criticism of the party’s internal decision-making processes.

Green Party leader Zack Polanski, who is Jewish, acknowledged that the motion was imperfect and said he would have preferred amendments to its wording. However, he defended its underlying criticism of Israel and accused Burnham of conflating opposition to Israeli government policies with antisemitism.

The decision has exposed significant divisions within the Greens, with senior figures warning that the policy risks alienating Jewish members and undermining the party’s electoral credibility.

The controversy also carries implications for Britain’s coalition politics. Labour currently governs alongside the Greens in several local councils.

British politics is increasingly fractured and while parliamentary majorities have generally been the case in the country, this now seems less certain, with current polling estimating that Labour would win 291 seats, short of the 326 needed for a majority in the 650-member lower house of the British Parliament, meaning that the party would likely need a coalition to remain in power. However, the Greens are only projected to win nine seats on current polling, meaning the two parties would still be short of a majority.

The chart below shows the seat projections based on current polling in the United Kingdom.