Green Party members have voted to back a controversial motion on Zionism and the future of Palestine, despite opposition from several senior figures within the party.

The motion, brought forward by the members' group Greens 4 Palestine, was approved at the party's annual conference in Brighton by 56 per cent of delegates, with 44 per cent voting against.

The motion defines Zionism as a political ideology advocating "an ethno-nationalist Jewish State" and calls for the establishment of a single Palestinian state with equal rights for all citizens, including Jewish people.

However, the motion also states that Zionism should be “treated as any other form of racism”, which critics point out could include practicing Jews and members of synagogues across Britain - making it impossible for them to join the Greens.

Westminster leader Ellie Chowns made a last-minute intervention calling for the motion to be defeated, while former party leaders Sian Berry, Adrian Ramsay and Carla Denyer were also critical of the proposal.

The party's deputy leaders were split, with Rachel Millward voting against the motion while fellow deputy leader Mothin Ali backed it.

Green leader Zack Polanski did not vote on the motion itself, but supported amendments that would have softened some of its language and added protections for Jewish members who identify as Zionists. Those amendments were rejected.

The motion was selected for debate after topping a ballot of issues submitted by party members for discussion at conference.

Following the vote, a joint statement was sent out which was originally attributed to the party’s five MPs and later reissued to include Mr Polanski and deputy leaders Mothin Ali and Rachel Millward.

The statement reads: “As Green Party leaders and MPs, we will always uphold universal human rights. We will never tolerate any form of discrimination or harassment.

“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.”

The Green Party's existing policy has supported either a one-state or two-state solution to the Israeli-Palestinian conflict if achieved through a democratic process. The newly approved motion specifically calls for a single Palestinian state and does not advocate a two-state settlement.

Under Green Party rules, the decision means the motion will now form part of official party policy.

In a statement following the vote, a 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.”

Only 1,835 members participated in the vote, despite the party having a membership of more than 200,000.