Northern Ireland’s first minister has resigned as tensions over the United Kingdom’s departure from the European Union triggered a fresh political crisis in the region.

Paul Givan stepped aside on Thursday after one of his ministers tried to block the inspection of goods arriving from other parts of the UK – a move that violates the Brexit agreement between the UK and the European Union.

“Today marks the end of what has been the privilege of my lifetime,” Givan, who spent less than a year as chief minister in the region’s devolved government, told a news conference.

The Brexit deal is roiling Northern Ireland once again because of disagreements about language designed to keep trade flowing on the island of Ireland.

Under the so-called Northern Ireland protocol, the UK agreed to inspect some goods entering Northern Ireland from England, Scotland and Wales. That angered many in Northern Ireland because it creates a barrier between the region and other parts of the UK.

“Our institutions are being tested once again,” Givan said as he resigned. They have “been impacted by the agreement made by the United Kingdom government and the European Union, which created the Northern Ireland Protocol.”

Northern Ireland is governed by a power-sharing executive created by agreements that ended decades of sectarian conflict in the region.

‘Extremely disappointing’

Givan was a representative of the largest party of voters who want to retain close ties to Britain, the Democratic Unionist Party. He shared power with Michelle O’Neill, the deputy first minister who represents Sinn Fein, which seeks to strengthen links to the Republic of Ireland.

Sinn Fein leader Mary Lou McDonald immediately called for new elections for the Northern Ireland Assembly. Elections are scheduled to be held in May.

“We cannot stagger on in the months ahead without a functioning executive, and Sinn Fein will not facilitate this,” McDonald said. Opinion polls suggest Sinn Fein will pass the DUP to become Northern Ireland’s largest party for the first time.

Brandon Lewis, the British government’s Northern Ireland secretary described Givan’s decision as “extremely disappointing”.

Northern Ireland Agriculture Minister Edwin Poots, a member of the DUP, ignited the crisis Wednesday when he ordered his staff to stop the inspections, saying they had not been authorised by the region’s power-sharing government.

The Republic of Ireland’s foreign minister, Simon Coveney, said Poots’ decision was “effectively a breach of international law” because the protocol is part of an international treaty. The republic is an EU member, and the Northern Ireland frontier is the bloc’s only land border with the UK.

“To deliberately frustrate obligations under that treaty would be a very serious matter indeed,” Coveney told Irish lawmakers late Wednesday. “It’s essentially playing politics with legal obligations.”

British Foreign Secretary Liz Truss was scheduled to hold a virtual meeting later Thursday with Maros Sefcovic, the EU’s chief negotiator on Brexit issues, as the two sides try to resolve differences over implementation of the protocol. Prime Minister Boris Johnson, who negotiated the Brexit deal, has called for the protocol to be renegotiated.

Mairead McGuinness, the Irish politician who serves as the European commissioner for financial services, told Irish broadcaster RTE that she also planned to speak with Truss and Sefcovic later Thursday.

“It’s very unhelpful,” she said. “We’re working tirelessly with the UK to find solutions.”