Northern Ireland’s Democratic Unionist Party leader, Jeffrey Donaldson, admitted on Saturday that his nationalist opponents, Sinn Fein, were on track for a historic election triumph.

“Certainly it looks at the moment as if Sinn Fein will emerge as the largest party,” He told Sky News that the DUP would refuse to join a future administration unless adjustments were made to the UK-EU trade pact after Brexit.

Donaldson requested that Prime Minister Boris Johnson “deliver on his word to honour the pledges he has made and take the appropriate action” on the Northern Ireland Protocol.

He urged “decisive action by the government to remove the Irish Sea border, because we don’t believe it is acceptable or necessary to have checks on goods moving within the United Kingdom”.

While Sinn Fein will get to nominate a first minister, Northern Ireland’s power-sharing government cannot form unless the DUP agrees to take part.

“I want a government in Northern Ireland, but it has to be one based on stable foundations,” Donaldson said.

“And the long shadow of the Northern Ireland Protocol is harming our economy, it’s harming political stability.”