The head of the Jewish Greens has said she may leave the party after it voted to adopt a policy that equates Zionism with racism and calls for Israel to be replaced by a single Palestinian state.

The motion says Zionism – the movement for a Jewish state – should be “treated as any other form of racism”. It calls for Israel to be replaced by a single Palestinian state “with equal rights for all”.

Some Jewish Greens have expressed concern that this will mean they could face disciplinary action for belonging to Jewish organisations that officially support Zionism, even synagogues. Supporters of the motion, which was led by a group called Greens for Palestine, have said this would not happen.

The chief rabbi, Ephraim Mirvis, described the motion as “poisonous antisemitism” and a “threat to British Jews and to Britain”.