The Trades Union Congress has voted at its annual conference to withdraw co-operation with Israeli organisations, including the Israeli trade union the Histadrut.
They said unions should "review their bi-lateral relations with all Israeli organisations, including Histadrut".
Although it was by no means a unanimous vote, it is still a significant step for the TUC.
It represents an unprecedented break between the British trade unions and the Histadrut , a relationship that goes back to the foundation of the state of Israel.
The amendment was proposed by Andrew Murray, chairman of the Stop the War Coalition, and seconded by Hugh Lanning, chair of the Palestine Solidarity Campaign.
It was criticised by the RMT and some unions have already said they will not end bilateral ties with the Histadrut.