The EU will be making a “historic misjudgement” if it fails to agree to rewrite the Brexit deal that covers trading arrangements for Northern Ireland, the UK warned on Tuesday.

In an uncompromising speech, UK Brexit minister Lord David Frost warned that “fractious” relations between the two sides would not find a new equilibrium unless the EU agrees to British demands to fundamentally rewrite the so-called Northern Ireland protocol in the withdrawal agreement.

He was speaking ahead of the publication on Wednesday of a new package of measures by the European Commission to try to ease the bureaucratic impact of the protocol.

The protocol, which sought to avoid the return of a hard border on the island of Ireland, has bedevilled relations between London and Brussels since it came into force in January.

“For the EU now to say that the protocol . . . can never be improved upon, when it is so self-evidently causing such significant problems, would be a historic misjudgement,” said Frost in a speech in Lisbon.

Business has complained about how the protocol requires customs and regulatory checks on goods going from Great Britain to Northern Ireland, and the arrangements were one of several factors blamed for fuelling violence on Belfast’s streets in April.

Northern Ireland’s pro-UK unionist politicians object to how their region, by being placed in the EU’s single market for goods, is treated differently to Great Britain.

Frost accused the EU of sometimes looking like it wanted post-Brexit Britain to fail, as he made clear the UK wants root and branch reform of the Northern Ireland protocol, including an end to the role of the European Court of Justice in oversight of the withdrawal agreement.

Citing the rejection of the Brexit deal by Northern Ireland’s unionist parties, Frost also repeated his threat that the UK would unilaterally suspend parts of the protocol using procedures set out in article 16 if the EU did not bend further.

“It is our responsibility to safeguard peace and prosperity in Northern Ireland, and that may include using article 16 if necessary,” he said.

The EU has said it will not renegotiate the fundamental tenets of the Northern Ireland protocol, but the bloc is prepared to find ways to reduce the volume of checks on goods.

EU diplomats believe the commission’s package of measures, outlined to them on Tuesday, go about as far as the bloc’s law allows.

To try to assuage unionist concerns, the commission is expected to propose that many foods from Great Britain will be allowed to enter Northern Ireland with significantly reduced checks, including chilled meats such as sausages, so long as they are labelled as for sale in the “UK only”.

Mairead McGuinness, Ireland’s EU commissioner who is in charge of financial services, said the measures would give answers to “the real practical problems on the ground for business”.

She urged the UK to listen to Northern Ireland’s business community and focus on the potential benefits the protocol could bring, including privileged access to the EU single market compared to companies in Great Britain.

“I hear the business community just shutting their ears to this political drama and they are saying . . . let us reap the rewards of access to the EU market while maintaining access to the United Kingdom. And I mean why not?” she said.

Simon Coveney, Ireland’s foreign minister, said the commission’s proposals were “practical” and came after “months of hard work, careful listening”. 

EU diplomats warned Frost’s rhetoric could backfire, and that any move which imperilled Ireland’s place in the EU single market would be met with a united response by the bloc’s 27 member states. “The Irish have got solidarity and we would like the same if we were in that position one day,” said one.

Sir Jeffrey Donaldson, leader of the Democratic Unionist party, the largest group in Northern Ireland’s devolved government, said the protocol needed to be “replaced” because it was undermining the region’s position in the UK.

“This is not a time for tinkering around the edges with temporary fixes,” he added in a statement. “We need a long-term solution.”

Additional reporting by Jude Webber in Dublin and Peter Wise in Lisbon