Israeli flags from a pro-Israel rally outside Green party conference venue in Brighton on Sunday.

The Greens have formally adopted a policy which equates Zionism with racism, a move that will dismay the bulk of the party’s MPs and has alarmed some Jewish members.

In a vote at the party’s annual conference in Brighton about whether to back a motion which calls for Zionism, the movement for a Jewish state to be “treated as any other form of racism”, it passed by 1,022 votes to 813.

The motion, which is now formal policy for the Greens in England and Wales, also calls for a single Palestinian state in place of Israel “with equal rights for all”.

In earlier voting, an amendment ensuring other parts of Green policy are updated to take account of the motion was backed. Three other amendments, including one that said the motion should not be used to “pressure, proscribe or discipline members based on affiliation with Jewish community institutions”, were voted down.

The primary motion, titled “Zionism is racism”, had been pushed by a group called Greens for Palestine, which encouraged non-party members to sign up to the party to make sure the policy was debated and adopted.

The motion argues that Zionism is necessarily racist as it “privileges one ethnic group on the basis of the subjugation of others”. It adds: “This motion is aimed at the political ideology and practice of Zionism, as defined, and not at the religious or ethnic background of those who may identify as Zionists. Not all Jews are Zionists and not all Zionists are Jews …“Zionism, as defined above, will be treated as any other form of racism, and this motion will be implemented by the anti-racism policy working group as appropriate and in accordance with its ordinary practice.” Some Jewish Greens have said privately they are worried the policy could make it difficult for them to remain in the party.

A poll by the group Jewish Greens found its membership was split over whether to oppose the motion, while 81% said they did not identify as Zionist. The group is expected to only comment publicly on the vote after consulting members.

There is considerable disquiet among some senior Greens who feel that Zack Polanski, who is Jewish, could have taken a stronger stance on the issue. The party leader, who missed the vote to campaign in Holborn and St Pancras where he is standing in a parliamentary byelection next week, has justified the motion’s argument by noting the extent of the death toll in Gaza during Israel’s assault on the territory.

Asked on Saturday if he believed Zionism was racist, Polanski told the BBC: “Well, in the motion, it is defined as the displacement and genocide of the Palestinian people. I think that is clearly racism.”

Four of the party’s five MPs have condemned the motion, as did Caroline Lucas, the former leader who was the Greens’ first MP.

Adrian Ramsay, who co-led the Greens before Polanski, said in a statement he would vote against it as it set out what sort of Palestinian state should exist, without taking into account the self-determination of Israelis and Palestinians. Siân Berry, another of the MPs, made the same point Carla Denyer, the Bristol Central MP who was co-leader with Ramsay, said the wording “risks alienating a significant proportion of Jewish people, including those who vehemently disagree with the Israeli government”.

Another Green MP, Ellie Chowns, said the motion “risks fuelling division, and risks undermining the party’s ability to advocate effectively for justice and peace”.

“Zionism is a contested concept with no single definition. If this motion passes, the party risks alienating many people, including in Jewish communities. Defining a highly personal and variable identity simply as racism risks reinforcing exactly the zero-sum politics we desperately need to get beyond.”