Israel said Thursday that the British Consulate in east Jerusalem has “ceased to function” in that capacity and that 20 staffers will leave the country, in what the Associated Press (AP) describes as the biggest diplomatic rift between the two close allies in decades.

The dispute began last month, when the United Kingdom banned trade with Israeli settlements in the occupied West Bank, which the UN and much of the international community consider illegal. A sign outside the consulate was taken down, but Britain said the building remains open and a core staff will continue to deliver “vital services” and work with Palestinians.