The European Union on Sunday rejected an incendiary claim by Prime Minister Boris Johnson that the bloc is plotting to destabilise the UK as another week of Brexit high drama beckoned, headlined by a stormy parliamentary debate in London.

The war of words escalated over a new British government bill that London admits is in violation of its EU divorce treaty -- legislation that has sparked a furious response from former prime ministers Tony Blair and John Major, as well as sitting MPs.

Johnson's claim that the 27-nation EU is plotting to choke off food supplies via crippling new trade barriers between Britain and Northern Ireland is "spin and not the truth," Irish Foreign Minister Simon Coveney told BBC television.

"There is no blockade proposed," he added, calling it "inflammatory language coming from Number 10 (Downing Street)."

Charles Michel, who heads the EU Council of government chiefs, said Britain's "international credibility" was at stake as both sides battle to unwind nearly 50 years of economic integration, following a deeply divisive referendum in the UK.

EU trade negotiator Michel Barnier insisted that a Northern Irish protocol in the EU treaty "is not a threat to the integrity of the UK", as claimed by Johnson in Saturday's Daily Telegraph newspaper.

The Irish Border
The Irish border is once again the crux of a Brexit showdown Photo: AFP / PAUL FAITH

Major and Blair, who led Britain through Northern Ireland's historic peace talks in the 1990s, wrote in the Sunday Times that the government's actions were "shaming itself and embarrassing our nation".

Backed by the EU, Ireland stresses the provisions for Northern Ireland were agreed by both sides to ensure fair competition after Brexit, and to comply with a 1998 peace pact that ended three decades of unrest in the province.

Johnson had accused the EU of threatening to tear the UK apart by imposing a food "blockade" between Britain and Northern Ireland, which is meant to enjoy a special status with the EU after Brexit.

Johnson said the EU's stance justified his government's introduction of the new legislation to regulate the UK's internal market and maintain access to Northern Ireland, after a post-Brexit transition period expires at the end of this year.

Boris Johnson
Boris Johnson claimed the EU wanted to impose a food "blockade" Photo: POOL / Stefan Rousseau

The food dispute centres on the EU's reluctance to grant Britain "third country" status, which acknowledges that nations meet basic requirements to export their foodstuffs to Europe.

The EU is worried that post-Brexit Britain could undercut its own food standards, as well as rules on state aid for companies, and infiltrate its single market via Northern Ireland.

After the latest round of trade talks last week in London, Barnier had said "many uncertainties" remained about Britain's food export regime after January 1, and "more clarity" was needed for the UK to enjoy third-country listing.

Barnier is due to meet again this week with his British counterpart David Frost in Brussels, days after the EU threatened Britain with legal action unless it withdraws its unilateral changes by the end of September.

Frost on Sunday replied to Barnier with a lengthy thread on Twitter that took details of their closed-door disagreements public.

Frost said Britain's food rules would stay exactly the same on January 1, but that Barnier's team had stated "to us explicitly in these talks that if we are not listed we will not be able to move food to Northern Ireland".

EU diplomats, and Johnson's many critics in Britain, suspect that the government is using the new legislation to jettison the entire framework of negotiations after failing to realise the treaty's full implications.

The bill will come up for its first debate in the House of Commons on Monday, and mutinous MPs are demanding its withdrawal and pressing for Justice Secretary Robert Buckland to resign.

"If I see the rule of law being broken in a way I find unacceptable then of course I will go," Buckland told the BBC.

"I don't believe we're going to get to that stage," he added, reiterating Johnson's view that the new bill is an "insurance policy" in the event of a Brexit "no deal" this year.

Copyright AFP. All rights reserved.