Simon Coveney has warned that Britain will “force the EU to respond” if Boris Johnson attempts to override the Northern Ireland Protocol amid fears of a trade war.
The Foreign Affairs Minister told thelast night there would be "consequences" if the UK took action in breach of its obligations under international law.
British ministers have threatened to defy the international Brexit agreement — which requires checks on some goods entering the North from England, Scotland, and Wales — claiming it is creating political instability in Northern Ireland.
Mr Coveney rejected this argument, noting that there is more than one community in the North.
“I think you’ve heard a similar message from myself and the Taoiseach in the last few days, and it is blunt, accurate, and fair," he said.
"It is in response to very aggressive briefing in the British media in the last week or so in relation to the Protocol.
“In my view, should they choose to unilaterally break international law and set side elements of the protocol, it will cause more problems than it will solve, which is why we’ve been so direct that it shouldn’t happen. I've asked them to engage in a professional way.
“This idea they didn’t know how the protocol would work is nonsense. We all knew exactly what we were signing up for," said Mr Coveney.
"We also agreed on an implementation strategy before it took effect. Now we’re focused on applying it with maximum flexibility but to also respect the legal text."
Mr Coveney is to meet British foreign secretary Liz Truss today in Brussels amid continuing tension between the EU and UK, with relations said to be at an all-time low.
“We have an obligation to the people in Northern Ireland to resolve the issues and not resort to sabre-rattling," Mr Coveney added.
The EU has said it is willing to set aside around 80% of the checks on goods entering the North from Britain if it can be proved they are consumed there.
“The British response has been, 'it's not enough, we’re going to break international law and not respect the democratic wishes of the people of Northern Ireland’,” Mr Coveney said.
Mr Johnson has said the UK will have a "necessity to act" if the EU is unwilling to reach a compromise.
The British prime minister — who travels to Belfast today for emergency talks with the North's parties — said his government remained open to "genuine dialogue" with Brussels.
However, amid fears of a looming trade war, he said that if there was no movement on the EU side, his government will set out its "next steps" in a statement to the UK parliament "in the coming days".
His warning comes amid reports that ministers could table emergency legislation as early as this week to override the protocol.