The UK government on Monday introduced legislation to rip up post-Brexit trading rules for Northern Ireland, despite the possibility that could spark a trade war with the EU.

London says it still prefers a negotiated outcome with the European Union to reform the Northern Ireland Protocol.

But with talks stalled, the bill proposes overriding the EU withdrawal treaty that the UK signed, although the government in London insists it is not breaking international law.

The EU quickly threatened legal action in response while Dublin called it "a particular low point in the UK's approach to Brexit".

Critics of the 'Northern Ireland Protocol' say it is disrupting trade and casting the territory adrift from the rest of the UK
Critics of the 'Northern Ireland Protocol' say it is disrupting trade and casting the territory adrift from the rest of the UK AFP / Paul Faith

US Secretary of State Antony Blinken said any solution must not threaten the US-brokered 1998 deal that has largely brought peace to the territory.

He urged British Foreign Secretary Liz Truss "to continue good faith negotiations with the EU to reach a solution that preserves the gains of the Belfast/Good Friday Agreement," a statement said.

The US has said any breach of the peace deal would threaten a bilateral trade deal with the UK.

That could not come at a worse time for the UK, which is grappling with inflation at 40-year highs and rising household bills that have left many Britons struggling to make ends meet.

UK Northern Ireland Secretary Brandon Lewis says changes are needed to the trade deal
UK Northern Ireland Secretary Brandon Lewis says changes are needed to the trade deal BBC via AFP / Jeff OVERS

London claims the new legislation will address "burdensome customs processes, inflexible regulation, tax and spend discrepancies and democratic governance issues" that are "undermining" peace in Northern Ireland and have paralysed its power-sharing government.

Truss spoke to European Commission Vice President Maros Sefcovic and Ireland counterpart Simon Coveney on Monday to inform them the bill was being introduced in parliament.

The UK government is proposing a 'green channel' for traders sending goods from England, Scotland and Wales to Northern Ireland
The UK government is proposing a 'green channel' for traders sending goods from England, Scotland and Wales to Northern Ireland AFP / Paul Faith

She called it a "reasonable, practical solution to the problems facing Northern Ireland".

But Sefcovic said that the EU would not renegotiate its divorce deal and that Brussels would now consider reopening a suspended "infringement procedure" against Britain, as well as opening fresh cases.

"It is with significant concern that we take note of today's decision by the UK Government to table legislation," he said in a prepared statement to reporters in Brussels.

Sefcovic tweeted earlier that he had warned the UK minister that "unilateral action is damaging to mutual trust and a formula for uncertainty".

Foreign Secretary Liz Truss called the proposed measures a 'reasonable, practical solution' to the problems in Northern Ireland
Foreign Secretary Liz Truss called the proposed measures a 'reasonable, practical solution' to the problems in Northern Ireland AFP / Niklas HALLE'N

Coveney told Truss the move marked "a particular low point in the UK's approach to Brexit" and was "deeply damaging to relationships on these islands and between the UK and EU".

"The UK's unilateral approach is not in the best interest of Northern Ireland and does not have the consent or support of the majority of people or business in Northern Ireland," he added.

But Prime Minister Boris Johnson insisted that the move was "the right way forward" and was needed to maintain the "balance and the symmetry" of the Good Friday peace agreement between pro-UK unionists and nationalists who want a united Ireland.

The pro-UK Democratic Unionist Party argues that the protocol's creation of an effective border in the Irish Sea is jeopardising Northern Ireland's status in the wider UK and makes a united Ireland more likely.

It is boycotting the local government in Belfast until the deal is scrapped or dramatically overhauled.

Northern Ireland's first minister-elect, Michelle O'Neill, of Irish nationalists Sinn Fein, said Johnson was "in clear breach of international law".

But DUP leader Jeffrey Donaldson welcomed the bill as "the kind of action that is required" to remove what he said were barriers to trade within the UK.

The protocol requires checks on goods arriving in Northern Ireland from England, Scotland and Wales, to prevent them from entering the EU's single market via the Republic of Ireland and to avoid a return to a "hard border".

Border infrastructure was a flashpoint during 30 years of violence over British rule in Northern Ireland and an open border was central to the peace deal.

The UK bill proposes scrapping most of the checks, creating a "green channel" for British traders to send goods to Northern Ireland without making any customs declaration to the EU.

The EU would have access to more real-time UK data on the flow of goods, and only businesses intending to trade into the single market via Ireland would be required to make declarations via a "red channel".

The EU would need to trust the UK to monitor the flow, London said, promising "robust penalties" for any companies seeking to abuse the new system.