Next week's Trades Union Congress will debate withdrawing all co-operation with Israeli organisations, including the giant Israeli trade union the Histadrut.
The unprecedented proposal is the subject of an amendment by the Public and Commercial Services Union (PCS), to a motion on the Middle East by super-union Unite.
The move would break a link between the British trade unions and the Histadrut that goes back to the foundation of the state of Israel.
The Israeli organisation is believed to be furious at the proposal and the Histadrut, in response, would almost certainly initiate moves to isolate Britain within the international trades union movement if the amendment is voted through. The Palestine General Federation of Trade Unions (PGFTU) has not called for the break and still has close, if sometimes strained, links with the Histadrut.
The amendment proposed by the PCS, whose deputy general secretary Hugh Lanning is also chair of the Palestine Solidarity Campaign, is a wide-ranging condemnation of UK foreign policy in South Asia, the Middle East, and North Africa, including the recent intervention in Libya. It is thought that Unite will back the amendment.
At the heart of the motion, which will be discussed next Wednesday, is a call for the British government to recognise Palestinian statehood.
It reads: "Since there can be no peace in the region without justice for the Palestinians, Congress endorses the call for the recognition of the state of Palestine and urges the British government to take all actions appropriate to help achieve this objective."
At the same time it calls for the immediate, unconditional resumption of peace talks and a reaffirmation of last year's TUC Congress decision to work closely with the Palestine Solidarity Campaign to build the campaign to "disinvest from, and boycott the goods of, companies who profit from illegal settlements, the Occupation and the construction of the Wall."
But it is the Histadrut-targeted amendment which is far more controversial. Although it calls only for a review of bi-lateral relations, there is concern among pro-Israeli trade unionists that this is a backdoor route to a full boycott of Israel itself.
Trade Union Friends of Israel has warned TUC General Secretary Brendan Barber that support for the amendment would end the British trades union movement's involvement in PGFTU-Histadrut activity.
Stephen Scott, director of Trade Union Friends of Israel, appealed for British trade unionists to vote down the amendment and work towards peace and cooperation. He said: "This position will only emasculate the TUC and the British trade union movement in the work to bring the Israeli and Palestinian workers together".
He added: "Where are the motions condemning the bloodshed in Syria, where there are no free trade unions? This attack on the Histadrut, the only democratic trade union movement in the Middle East, can only be judged as an act of discrimination - because they are Israeli".
As party conference season begins, supporters of Israel will look to Labour leader Ed Miliband to clarify the position laid out in his leadership acceptance speech last year, when he attacked Israel over the Turkish flotilla incident without reference to Hamas terrorism.
Labour Friends of Israel, reinvented as a membership organisation under its chair John Woodcock MP, will debate the "Progressive Case for Israel" at its fringe event this year and Ed Miliband is due to speak at the LFI conference reception.