The EU is demanding urgent talks with the UK after the government published a bill that would override the Brexit deal despite admitting it will break international law.
European Union Commission vice president Maros Sefcovic said he was seeking an urgent meeting of the joint EU-UK committee so the British could “elaborate” on their plans.
Speaking at a news conference in Brussels, Mr Sefcovic said he had raised his concerns in a phone call with Cabinet Office minister Michael Gove.
He said: “The Withdrawal Agreement is not open for renegotiation and we expect the letter and the spirit of the Withdrawal Agreement will be fully respected."
Questions are being raised about why Boris Johnson, who championed his 'oven ready' deal and placed it at the centre of this general election campaign, now wants to take such drastic measures to ditch it.
ITV News Political Correspondent Carl Dinnen discusses why the bill is so controversial
The First Minister of Scotland Nicola Sturgeon labelled the UK government "a bunch of incompetent and unscrupulous chancers."
She questioned why they wanted to ditch the withdrawal agreement they were championing months earlier and trash the UK's international reputation.
The new Internal Market Bill would give the British government the power to dictate how goods are moved around the United Kingdom, particularly between Northern Ireland and the mainland after the end of the Brexit transition period.
The government says if the Brexit talks fail the current withdrawal agreement leaves that power in the hands of the EU, which could limit the UK's ability to trade within itself.
The bill would get rid of the requirement for new customs arrangements in Northern Ireland.
ITV News Political Correspondent Carl Dinnen said: "It says in black and white that the provisions of the bill will take effect even if they are inconsistent or incompatible with international or other domestic law."
Downing Street has sought to justify the Bill to override parts of Boris Johnson’s Withdrawal Agreement, saying the deal was written “at pace” in “the most challenging” circumstances.
In the Commons, Mr Johnson defended the legislation, saying it provided a “legal safety net” to protect against “extreme or irrational interpretations” of the Northern Ireland provisions of the agreement which could lead to the creation of “a border down the Irish Sea”.
European leaders have been expressing concern about the new direction the UK government is taking.
President of the European Union Commission Ursula von der Leyen said she was "very concerned about announcements from the British government on its intentions to breach the Withdrawal Agreement.
"This would break international law and undermines trust."
President of the European Council Charles Michel said: "The Withdrawal agreement was concluded and ratified by both sides, it has to be applied in full.
"Breaking international law is not acceptable and does not create the confidence we need to build our future relationship."
The Irish Taoiseach Micheál Martin said he would be raising the issue in a call with the prime minister later.
He said: "It is very regrettable that Northern Ireland has been dragged back into this and this is not an acceptable way to conduct negotiations."
After Northern Ireland Secretary Brandon Lewis admitted the current government's plans would break international law in a "specific and limited way", it caused alarm across the UK's political spectrum.
Former Prime Minister Theresa May criticised the move saying it would make the UK and untrustworthy country.
The head of the UK's legal department and one of the country's most senior lawyers quit over the proposals.
Several senior Conservative backbenchers, included the chair of the justice committee Sir Bob Neill reacted with alarm to the news.
Sir Bob said any plan to "break international law sits ill for a country that has always prided itself on upholding the rule of law."
Labour's Louise Haigh described the admission as “absolutely astonishing” and warned it would “seriously undermine” the UK’s authority on the international stage.
The Prime Minister’s official spokesman said: “The Withdrawal Agreement and the Northern Ireland Protocol aren’t like any other treaty.
“It was agreed at pace in the most challenging possible political circumstances to deliver on a clear political decision by the British people with the clear overriding purpose of protecting the special circumstances of Northern Ireland.
“It contains ambiguities and in key areas there is a lack of clarity. It was written on the assumption that subsequent agreements to clarify these aspects could be reached between us and the EU on the details and that may yet be possible.”
A former UK official told ITV Political editor Rober Peston: “I have been presuming that their inability to detail the proposed [food standards] regime is down to intense US pressure and the split in HMG as to whether to diverge radically from EU standards or not.
"You can only avoid the choices and trade offs for so long.
"But no partner - EU or US - takes political assurances in trust.
"It’s about legal texts and binding commitments in treaties now”.