Boris Johnson is tonight on a fresh collision course with Brussels after the EU said it would not renegotiate the Northern Ireland protocol.
European Commission vice-president Maros Sefcovic also threatened legal action against the UK as the government published its long-awaited legislation to unilaterally rip up the Brexit deal the prime minister signed barely two years ago.
The Northern Ireland Protocol bill would give ministers the power to over-ride rules imposing customs checks on goods travelling between Northern Ireland and the rest of the UK.
The government says the move is essential to preserve the Good Friday Agreement, which ended 30 years of sectarian bloodshed in Northern Ireland.
However, critics claim that would break international law as it would contravene the EU withdrawal agreement negotiated between the government and Brussels.
But a paper outlining the government’s legal position said they were envoking the “doctrine of necessity”, which ministers claim allows countries to break international treaties, in order to protect the Good Friday Agreement.
Johnson described his plans as a “relatively trivial set of adjustments in the grand scheme of things” and called on the EU to come back to the negotiating table to reach a fresh agreement.
But responding to the draft legislation, Sefcovic said: “Renegotiation of the protocol is unrealistic. No workable alternative solution has been found to this delicate, long-negotiated balance.
“Any renegotiations would simply bring further legal uncertainty for the people and businesses in Northern Ireland. For these reasons the European Union will not renegotiate the protocol.”
He also raised the prospect of Brussels retaliation, which could take the form of a damaging trade war with the UK.
“It is with significant concern that we take note of today’s decision by the UK government to table legislation disapplying core elements of the protocol,” he said. “Unilateral action is damaging to mutual trust.
“In particular, the protocol provides business operators in Northern Ireland with access to the EU single market for goods. The UK government’s approach puts this access – and related opportunities – at risk.
“Our aim will always be to secure the implementation of the protocol. Our reaction to unilateral action by the UK will reflect that aim and will be proportionate.”
Foreign secretary Liz Truss said the bill will “support political stability in Northern Ireland”.
“It will end the untenable situation where people in Northern Ireland are treated differently to the rest of the United Kingdom, protect the supremacy of our courts and our territorial integrity,” she said.
“This is a reasonable, practical solution to the problems facing Northern Ireland.
“It will safeguard the EU single market and ensure there is no hard border on the island of Ireland.
“We are ready to deliver this through talks with the EU. But we can only make progress through negotiations if the EU are willing to change the protocol itself – at the moment they aren’t.
“In the meantime the serious situation in Northern Ireland means we cannot afford to allow the situation to drift. As the government of the whole United Kingdom, it is our duty to take the necessary steps to preserve peace and stability.”