Speaking at Queen’s University in Belfast on Friday, Sefcovic, who presides over Britain and the EU’s relationship after Brexit, said a renegotiation of the protocol, “would mean instability, uncertainty and unpredictability in Northern Ireland”.

The senior Brussels official stated that the bloc had “been going through our rules with a fine tooth comb to respond to outstanding problems with creative and solid new solutions” in order to resolve the grievances over the trade deal.

Sefcovic, however, said that “the spirit of compromise needs to be a mutual one”, adding that the protocol is not the “problem”. Instead, he called it “the only solution we have.”

The remarks came after Jeffrey Donaldson, the leader of Northern Ireland’s Democratic Unionist party, threatened on Thursday to collapse the Stormont government unless there are big amendments to the protocol.

Britain’s exit deal with the EU has meant that Northern Ireland has been cut off from the UK mainland, with the province separated by a customs border down the Irish sea. The measure was implemented as an alternative to imposing a hard frontier on the Irish island.

Brussels and Britain have been embroiled in disputes to amend the deal. In July, the UK’s Brexit Minister David Frost warned the bloc that “we cannot go on as we are” and begged for a new deal that embodies more of a “sense of genuine and equitable partnership.”

Earlier this year, violence erupted in Northern Ireland over the post-Brexit protocol, resulting in dozens of police officers being injured during riots that were the biggest display of unrest there in decades.