LONDON: The leader of Northern Ireland’s biggest party on Thursday suspended cooperation with Dublin and warned he might collapse the province’s devolved government in protest at a UK-EU protocol governing post-Brexit trade.

Democratic Unionist Party (DUP) leader Jeffrey Donaldson demanded “significant and substantial changes” to the Northern Ireland Protocol, under which London agreed to checks on goods crossing the Irish Sea as part of its drawn-out divorce from the European Union.

Donaldson took over the faction-ridden DUP in June and is due to meet with EU Commission vice-president Maros Sefcovic, who has insisted the EU will not renegotiate the protocol.

But the DUP leader said it was “a matter of political reality, that our political institutions will not survive a failure to resolve the problems that the protocol has created”.

“Let me be clear: if the choice is ultimately between remaining in office or implementing the protocol in its present form, then the only option for any unionist minister would be to cease to hold such office,” he said, warning the DUP might trigger new elections in Northern Ireland.

Donaldson said the DUP was pulling out of a cross-border dialogue council with the government of EU member Ireland — “Strand Two” of a 1998 peace deal that ended three decades of violence over British rule in Northern Ireland.

“In such circumstances unionists cannot be expected to operate Strand Two as though nothing had changed,” he said.

The Northern Ireland Protocol came into effect on January 1, when the United Kingdom left the European single market and customs union.

It involves checks on goods arriving in Northern Ireland from mainland Great Britain — England, Scotland and Wales — to stop items entering the EU by the backdoor via Ireland.