LONDON — The leader of Northern Ireland’s largest British unionist party heightened post-Brexit political tensions on Thursday, saying the U.K.’s divorce deal with the European Union could collapse the Belfast government and trigger a new era of violence and instability.

Democratic Unionist Party leader Jeffrey Donaldson threatened to pull his party out of the power-sharing administration if the rules for Northern Ireland trade agreed by the U.K. and the EU last year are not fundamentally changed within weeks.

In a speech in Belfast, he said the agreement known as the Northern Ireland Protocol “fundamentally undermines … the economic integrity of the United Kingdom and Northern Ireland’s position in it.”

“We are totally opposed to the protocol as it presently exists,” Donaldson said.

He said that the problems must be resolved “in weeks and not months or years,” and said DUP ministers would quit Northern Ireland’s Protestant-Catholic power-sharing administration rather than implement the deal in its present form. That would effectively collapse the government, which is run by the DUP and Irish nationalist party Sinn Fein.

He also said DUP ministers would boycott regular meetings with politicians in Ireland as a protest against the new rules.

“I say not as a threat, but as a matter of political reality that our political institutions will not survive a failure to resolve the problems that the protocol has created,” said Donaldson, who was elected DUP leader two months ago.


The regulations are intended to prevent goods from Britain entering the EU’s tariff-free single market while keeping an open border between Northern Ireland and EU member Ireland — a key pillar of Northern Ireland’s peace process. But the checks have angered Northern Ireland’s unionists, who say they impose burdensome red tape on businesses and weaken Northern Ireland’s ties with the rest of the U.K.

Tensions over the new rules contributed to a week of street violence in Northern Ireland cities in April that saw youths pelt police with bricks, fireworks and gasoline bombs.

Donaldson said the violence had died down, “but I fear that unless we grapple with this issue, this will prove to be merely a pause, rather than an end to the disorder.”

Sinn Fein leader Mary Lou McDonald called Donaldson’s stance a “reckless, irresponsible and short-sighted election stunt.” Doug Beattie of the Ulster Unionist Party, the DUP’s rival for unionist votes, said Donaldson’s “threats” were counterproductive.

“We continue to lobby rather than threaten,” he said.

The EU’s chief Brexit official, Maros Sefcovic, urged all sides to “dial down the political rhetoric” and “work on the concrete problems.”

Britain and the EU both say they want to fix the problems, but they remain far apart on solutions.

Britain’s Conservative government has accused the bloc of being needlessly “purist” in implementing the rules. The U.K. is seeking ultimately to remove most checks, replacing them with a “light touch” system in which only goods at risk of entering the EU would be inspected.

In the meantime, Britain has postponed indefinitely the start of many checks on goods going to Northern Ireland, which were due to be phased in after the U.K. left the EU’s economic embrace at the end of 2020.

The EU says it won’t renegotiate the agreement and is calling for Britain to implement the deal that Prime Minister Boris Johnson agreed to.

The two sides have agreed to keep talking. Sefcovic, the European Commission vice-president Maros Sefcovic, is visiting Northern Ireland on Thursday and Friday to meet with businesses and politicians including Donaldson.