Britain's Brexit minister threatened on Monday to trigger a contentious break clause in the United Kingdom's divorce deal with the European Union－a move that would send the UK's already chilly relations with its huge neighbor into a deep freeze.

During a gathering of the ruling Conservative Party, Brexit Minister David Frost said the Brexit deal was undermining peace in Northern Ireland and causing "instability".

The crisis straining UK-EU relations stems from trade arrangements for Northern Ireland, the only part of the UK that has a land border with the 27-nation bloc. The divorce deal means customs and border checks must be conducted on some goods moving between Northern Ireland and the rest of the UK.

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 said they impose burdensome red tape on businesses and weaken Northern Ireland's ties with the rest of the UK.

Britain accuses the EU of being needlessly "purist" in implementing the agreement, known as the Northern Ireland Protocol, and said it requires major changes for it to work.

Blaming the bloc's "heavy-handed actions", Frost said the protocol itself was undermining Northern Ireland's 1998 peace agreement.

EU officials are likely to greet Frost's ultimatum－and his description of Britain's EU membership as a "long bad dream"－with disdain.

The EU blames Britain for the disruption, accusing it of trying to renege on a legally binding deal it signed up to.

A severe shortage of truck drivers, due in part to a post-Brexit exodus of European workers, has snarled British supply chains, leaving gaps on supermarket shelves, fast-food chains without chicken and gas pumps dry. Scores of soldiers have been drafted in to drive fuel tankers after more than a week of gas shortages.

On Sunday, Prime Minister Boris Johnson refused to return Britain to its "broken" pre-Brexit economy which he said was overly reliant on cheap foreign labor, calling the recent chaos "a period of adjustment".

Meanwhile, the Conservatives announced on Monday that all of Britain's electricity will come from renewable sources by 2035, saying the move would help end the country's reliance on imported fuel.

Agencies and Julian Shea in London contributed to this story.