Stormont’s Agriculture Minister Edwin Poots has ordered a halt to Brexit agri-food checks at Northern Ireland ports required under the terms of the Northern Ireland Protocol.
Mr Poots said he had received legal advice which stated he could order a halt to Northern Ireland Protocol checks.
Foreign Affairs Minister Simon Coveney has described the proposed move by Mr Poots as "effectively a breach of international law".
Mr Coveney tweeted: “Put simply, the British Government has an obligation to comply with International law. Surely that’s not too much to ask as we all work to find agreement on flexible and pragmatic implementation of the Northern Ireland Protocol.”
Britain’s Secretary of State for Northern Ireland Brandon Lewis confirmed the UK government will not intervene in the decision by Mr Poots.
Mr Lewis told ITV it was a “matter for the Northern Ireland Executive” and said it was “within their legal remit”.
Last week the UK’s Foreign Secretary Liz Truss also said the UK wouldn’t step in if Mr Poots moved to halt checks.
Mr Lewis said: "Obviously we'll be looking at the out workings of that, exactly what the legal advice is they have taken.
"One of the frustrations is, this I have to say, is something we have been saying to the European Union for some time, was the kind of thing that we could see happening.
"It's exactly the sort of thing we have been warning about, in terms of the stability of the Executive and the decisions the Executive ministers will take in order to ensure that products can move from Great Britain to Northern Ireland in a way that they always have done."
Speaking in the Seanad on Wednesday evening, Mr Coveney said the Northern Ireland Protocol is part of an international agreement that was agreed and ratified by EU and UK and that its implementation is part of international law.
"To deliberately frustrate obligations under that treaty would be a very serious matter indeed, it's essentially playing politics with legal obligations, and I certainly hope it doesn't happen as threatened and described," he told senators.
He added that the move was "really unhelpful", "far more about politics" and that the Government would be following the matter closely.
Speaking at Stormont earlier, Mr Poots said: “I have taken legal advice in relation to my position from senior counsel. Earlier today I received that legal advice.
“It stated that at present there is presently no Executive approval for SPS checks. The implementation of SPS checks requires Executive approval.
“A decision to initiate or continue such checks could not be validly taken in the absence of Executive approval.
“The advice concluded that I can direct the checks to cease in the absence of Executive approval.
“I have now issued a formal instruction to my permanent secretary to halt all checks that were not in place on December 31, 2020, from midnight tonight.
“I will prepare a paper for Executive consideration in the near future to seek agreement on a way forward.”
Mr Poots sought the legal advice after a failed bid to secure the wider approval of the Stormont Executive to continue checks on agri-food produce arriving in Northern Ireland from Great Britain.
The minister says that in the absence of Executive approval he no longer has legal cover to continue the documentary checks and physical inspections.
His move to seek a ministerial vote at the Executive last week was branded a stunt by other parties.
They insist the Executive has already agreed that Mr Poots’ department has responsibility for carrying out the checks and he does not have the authority to halt processes that are required under the terms of the Brexit Withdrawal Agreement, an international treaty.
Responding to the move by Mr Poots, an Irish Government source said it was "blatant electioneering".
They said the move was "a stunt more connected to the election and his own de-selection than anything to do with Brexit given that business in Northern Ireland is doing so well. The protocol is international law as passed by the palace of Westminster and the UK Government will need to step in here".
It is yet unclear whether the senior civil servant in his department, Anthony Harbinson, will comply with the order.
DUP rivals at Stormont insist the civil service has a duty to comply with Stormont's legal obligations to carry out the checks under the terms of the Brexit Withdrawal Agreement.
Deputy First Minister Michelle O’Neill of Sinn Féin claimed the move was an attempt to “unlawful interfere with domestic, and international law”.
"DUP fixated on their own priorities, which are clearly at odds with where the wider community is at. Health, jobs, housing, cost of living crisis is where the rest of us are focused,” she tweeted.
Alliance Party leader Naomi Long claimed people are “tired of this grandstanding and instability”.
"Edwin received clear legal advice in March 2020 when he first tried this stunt. Executive was clear, as was @DefraGovUK, that @daera_ni is obliged by law to undertake these checks,” she posted on social media.
Alliance MLA John Blair - the DUP were “addicted to disruption”.
“Step up and do the job or step aside,” he said.
SDLP MLA Matthew O’Toole said: “Nothing to do with the people or businesses of NI and everything to do with the DUP and their horrible Brexit mess they've got themselves into.
“Chaos, ignoring the law, putting party interest before public interest. And it won't work.”
In response, TUV leader Jim Allister welcomed the move but questioned how long it took Mr Poots to act.
“The fundamental question though remains, why did it take a year to do this - a year which included excuses and justifications for the very checks Minister Poots now abandons,” said Mr Allister.
“There is nothing like an election to focus minds.
“A major part of TUV’s function will be to ensure there is no backsliding on this issue, given that implementing for a full year that which has now been stopped does not generate confidence."