LONDON — Britain set itself on course for a new confrontation with the European Union on Tuesday by demanding the replacement of one of the most complex and vexing components of Brexit: the status of Northern Ireland.
In a speech to diplomats in Lisbon, David Frost, the Conservative government’s Brexit minister, asked for an overhaul of an agreement on post-Brexit trade rules for Northern Ireland, which is part of the United Kingdom but shares a politically sensitive land border with Ireland, a European Union country.
The move is a serious escalation in a simmering dispute over how Northern Ireland fits into the British withdrawal from the European Union. Mr. Frost’s proposed new text for the trade rules, called the Northern Ireland protocol, discards some elements that Prime Minister Boris Johnson agreed to less than two years ago and contains ideas the European Union has already rejected.
“We now face a very serious situation — the protocol is not working,” Mr. Frost said, arguing that instead of protecting a fragile peace process in Northern Ireland, the agreement was doing the opposite.
“The protocol represents a moment of E.U. overreach, when the U.K.’s negotiating hand was tied, and therefore cannot reasonably last in its current form,” Mr. Frost said, adding that it had been drawn up in extreme haste and that for the Europeans to reject the idea of changing it “would be a historic misjudgment.”
His speech served as something of a pre-emptive strike, coming just one day before the European Commission, the bloc’s executive body, is scheduled to present its own plans to resolve the difficulties it acknowledges have arisen with trade mainly between Britain and Northern Ireland.
Though soft-spoken and personable, Mr. Frost is a hard-liner whose aggressive negotiating style has been welcomed by Brexit supporters who believed that Mr. Johnson’s predecessor, Theresa May, was pushed around by Brussels. So, few were surprised that his speech raised the temperature on an inflammatory issue.
But significantly, Mr. Frost also called for a change to the role of Europe’s top court in adjudicating disputes — an abstract but politically sensitive issue over which the European Union is highly unlikely to concede.
That has prompted speculation that the demand is a bargaining chip to be traded for other concessions. An alternative theory is that it is designed to provoke a full-scale crisis that could lead to Mr. Johnson suspending part of the protocol, blaming the European Union and stoking pro-Brexit sentiment at home.
That would likely prompt retaliation from the European Union and possibly a trade war with the 27-nation bloc that Britain officially left in January 2020.
Designed to avoid resurrecting a hard border between Northern Ireland and Ireland, the protocol has led to checks on goods flowing from Britain to Northern Ireland.
That is to protect the integrity of the European Union’s giant single market of which Ireland is a part. But it has infuriated unionists in Northern Ireland who see their place within the United Kingdom as central to their identity and who resent checks on goods flowing from mainland Britain, which is part of the same country.
Mr. Johnson has the ability to suspend parts of the protocol under Article 16 of the Brexit agreement, but he is considered unlikely to do so before the climate summit, COP26, Britain is hosting in Glasgow from Oct. 31 through Nov. 12.
Discarding some of the protocol could also exacerbate tensions between Mr. Johnson and President Biden. The American president is proud of his Irish heritage and has made clear his commitment to the peace process in Northern Ireland that culminated in the Good Friday Agreement, struck in 1998 after decades of bloody conflict known as “The Troubles.”
Though some analysts believe Mr. Johnson wants to walk away from the protocol to please Brexit hard-liners at home, others see Tuesday’s speech by Mr. Frost more as a tactical intervention designed to minimize the influence of Brussels over any part of Britain, and maximize British sovereignty.
“Frost — who is a convinced Brexiteer — sees this attempt to renegotiate or adjust the protocol as the final means to weaken the ties that remain between the U.K. and the E.U.,” said Katy Hayward, a professor of political sociology at Queen’s University, Belfast.
Britain, she added, seemed to be “trying to wrangle the last bits of sovereignty from the E.U.”
Tuesday’s speech follows months of tension over impediments to trade between Britain and Northern Ireland, including the flow of some goods like chilled meats, a rift that became known as the “sausage wars.” In recent days that gave way to open sniping during which the Irish foreign minister, Simon Coveney, questioned whether Britain actually wanted an agreement, and Mr. Frost accused his European counterparts of refusing to listen.
Britain argues that the protocol is being implemented in an unnecessarily heavy handed way, while European officials accuse Mr. Johnson of breaking an agreement he made himself.
Answering questions after his address on Tuesday, Mr. Frost said that when Britain agreed to the protocol, it knew it was taking a risk. “We hoped that we were wrong and that the protocol would work,” he said. “It turned out we were right.”
For its part the European Union has repeatedly rejected Britain’s calls for a renegotiation of the agreement. It particularly opposes the removal of the Court of Justice of the European Union, based in Luxembourg and the bloc’s highest court, as the final arbiter of disputes.
Responding on Monday to excerpts from the speech that were released on Saturday for the British media, the spokesman for the E.U. Commission, Eric Mamer, described London’s demand to remove the court as unacceptable and “ground that we have covered a million times.”
Brussels often emphasizes that this British government signed the deal, which Mr. Frost himself negotiated, and which is now international law.
Another commission spokesman, Daniel Ferrie, said that oversight of European courts was essential to provide legal coherence and a functioning business environment throughout the single market.
Removing the court, Mr. Ferrie said, “would effectively mean cutting Northern Ireland off from the E.U.’s single market and related opportunities.”
On Wednesday, the commission will make proposals to smooth implementation of the protocol. Those measures are expected to include easing of food and plant safety checks to soften restrictions on trade in chilled meat from Britain into Northern Ireland. It may also ease some customs checks and checks on the supply of medicines.
The commission will also propose some ideas on how to engage citizens, business owners and politicians from Northern Ireland in oversight of the deal.
But Mr. Frost’s intervention suggests that such concessions will hardly be sufficient, setting the scene for several weeks of tense negotiation.
Ms. Hayward said that the risk for Northern Ireland was that Mr. Frost’s approach would do little to reassure the unionist community about the security of their place in the United Kingdom, while raising unrealistic expectations about the prospects of a completely new agreement.
“If you were to prioritize the peace process above all else when you are approaching the matter of the protocol and talks with the E.U., you wouldn’t go about it the way the British government has gone about it,” she added.
Stephen Castle reported from London and Steven Erlanger from Brussels.