The National Union of Students has adopted a vehement anti-Israel policy in a move that has stunned Jews on campus.
A motion, agreed by NUS executive officers on Tuesday, pledged to send British students on future flotillas to Gaza, build links with the Hamas-backed Islamic University of Gaza, twin British student unions with Palestinian universities, and called for the right to return for all Palestinian refugees.
The Union of Jewish Students and the Board of Deputies called on NUS president Aaron Porter to "immediately revoke the policy" and "return to the mainstream of student politics".
An NUS spokesman said Mr Porter and the union stood by the executive committee's decision and declined to comment further.
The motion was due to be discussed at the NUS national conference last month, but delegates agreed it should be resolved by the executive committee. It was passed at the committee's meeting after just 20 minutes of debate. Mr Porter did not vote as he was chairing the meeting.
A member of NUS's Black Students' Committee led the argument in favour of the motion, backed by students from nine universities including SOAS, Essex, Sussex and Bradford.
The motion makes no reference to Hamas, but acknowledges Archbishop Desmond Tutu's likening of Israel to apartheid South Africa, and former UN relief agency head John Ging's belief that conditions in Gaza represent a "medieval siege".
The sudden u-turn shocked Jewish students. UJS has enjoyed a period of good relations with NUS in recent years, with both Mr Porter and predecessor Wes Streeting supporting UJS's work and discouraging anti-Israel sentiment within their union.
Under their leadership, NUS refused to condemn Israel's Operation Cast Lead in Gaza in 2009 and Israel's actions during the Gaza flotilla incident a year ago in which nine Turkish activists died.
UJS campaigns director Carly McKenzie said: "This is such a regressive move when NUS is taking so many steps forward with regard to hate speech and its negative impact on campus.
"NUS needs to take the impact of aggressive anti-Israel motions such as this seriously. This is not just NUS taking a side on a heavily-polarised conflict, irresponsible though that is. It is NUS taking actions that isolate Jewish students from their national movement. A move like this just catapults NUS back to the fringes."
A Board of Deputies spokesman said: "This motion will not contribute to bringing peace to the Middle East. It will only serve to undermine attempts to improve campus relations and will leave Jewish students and those who support Israel feeling marginalised and abandoned by the very union which is meant to protect, defend and represent them."
Kanja Sesay, NUS Black Students' Officer, said: "It is a victory that NUS is finally standing in solidarity with the Palestinians and supporting their freedom. Winning this policy has been a long struggle."
The Palestine Solidarity Campaign said the new NUS policy was a "victory for tens of thousands of students" and said it looked forward to working with the union to implement it.
The University of London Union - Europe's biggest student union - voted on Wednesday to adopt a full boycott, divestment and sanctions policy against Israel.