The Green Party has called for the JNF to be stripped of its charity status and has pledged to sign up to a campaign which calls the charity "racist".
Delegates voted unanimously in favour of a motion condemning JNF's activities and denouncing its "claims to be an ecological agency" at the England and Wales party's spring conference on Sunday.
The motion was proposed by Deborah Fink, co-founder of Jews for Boycotting Israeli Goods.
She told the conference that the JNF was responsible for a "greenwash" and was a "major impediment" to Green Party policy on the Middle East.
Members supported the motion's criticism of "the JNF's policy of planting trees to hide the results of ethnic cleansing and its objective of facilitating Israeli colonialism in Palestine".
The party now will add its name to the list of signatories to the Stop the JNF Campaign, a group which calls the charity "racist" and "colonialist".
JNF chairman Samuel Hayek responded: "The motion passed by the Green Party is not just an attack on the JNF, but is also an attack on Israel and its people. The allegations are not new and they do not have any grounding in reality."
A motion was also put to the conference offering guidance on definitions of antisemitism to help party members "avoid antisemitic statements in political discourse". Proposed by the Greens' Liverpool branch, it was not passed due to arguments over re-wording and the need for "greater clarity".
Green Party member Terry Gallogly is an organiser of the Stop the JNF Campaign and chair of York Palestine Solidarity Campaign. He said the Greens' adoption of the policy was "a message to the JNF that their days are numbered - we won't tolerate their abuse of charity status in the UK to fund a system of land theft and racism against Palestinians".
The Charity Commission has previously rejected the campaign's calls for the JNF's charitable status to be revoked but Prime Minister David Cameron resigned as a patron of the JNF last year.
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