Stormont’s Agriculture Minister would be acting unlawfully if he moved to unilaterally halt Brexit checks at Northern Ireland’s ports, Michelle O’Neill has warned.

Northern Ireland’s deputy First Minister also said the senior civil servant in Edwin Poots’ department could not follow any order from Mr Poots to end checks, as it would be in contravention of the law and would not have the approval of the wider Stormont Executive.

However, DUP First Minister Paul Givan offered a very different interpretation of the potential action being considered by his party and constituency colleague, insisting there was a “sound legal basis” for Mr Poots’ position.

The prospect of Mr Poots attempting to halt the checks required under the Northern Ireland Protocol has emerged after he conceded a recent legal challenge on the issue.

A group called Unionist Voice Policy Studies had threatened to judicially review Mr Poots after claiming that the ongoing port checks on goods arriving from GB are unlawful because they have not received the wider approval of the Stormont Executive.

Under Stormont rules, ministerial decisions deemed “significant” should be referred to the collective administration.

Conceding the legal challenge before it materialised into a judicial review, Mr Poots has stated an intent to bring a paper to the Executive asking for approval to continue the checks.

Such a move would raise the potential for the DUP to wield a veto to deny authority for the checks. However, the matter is unlikely to ever reach the Executive for debate, as Sinn Fein is set to use its veto to block it getting on the agenda.

If Sinn Fein does prevent the issue reaching the Executive, Mr Poots has signalled an intent to order a halt to the checks, contending that he would not have the legal authority to continue them.

Questioning Mr Poots’ assertions, Ms O’Neill insisted the Executive had decided long ago that the responsibility for implementing the checks lay with the Agriculture Minister.

She said the minister had a legal responsibility to implement the checks.

Ms O’Neill also made clear that the NI Civil Service also has a responsibility to act legally and she said Department of Agriculture, Environment and Rural Affairs (Daera) permanent secretary Anthony Harbinson would have to ensure checks continued, even if the minister ordered otherwise.

“For Edwin Poots to take any unilateral action would be unlawful, there is a legal responsibility on him to implement the checks and to make the protocol work,” she said.

“There’s also a very clearly stated Executive policy that it is the Daera minister’s responsibility to ensure that that happens, that was agreed by all Executive parties, including the DUP, so they should stop speaking out of both sides of their mouths, join the rest of the parties who are trying to navigate our way through making the protocol work, iron out the kinks and deal with all the other challenges that we have – dealing with the pandemic, making sure that we deal with health waiting lists, that’s where the rest of us are focused and the DUP are constantly the outlier here.”

She added: “There’s a distinct lack of honesty from the DUP the whole way through the Brexit debate. There is no room for Edwin Poots to stop the checks, there is a legal responsibility on that department, and therefore the permanent secretary will ensure – as he has done previously (when Dr Denis McMahon was permanent secretary), Edwin Poots has played this card previously and failed – those things need to be implemented and the permanent secretary will make sure that happens.”

Mr Givan insisted the checks could only continue if the Executive agreed to it in the present day.

“The Agriculture Minister is going to bring forward a paper to the Executive,” he said.

“Whether it’s put on the agenda or not, it does not change the reality around these checks that are taking place being controversial – that requires Executive approval if a minister is wanting to continue to do that, so Edwin will bring forward that paper in due course.

“And we’ve had new case law which has very much established that responsibility upon Executive ministers that where there are cross cutting and controversial issues that should come to the Executive for the Executive to take a decision.

“So it will be for obviously Sinn Fein in the first instance to decide if it comes on the agenda.

“This paper will be seeking approval for the continuation of what is happening, so it would be strange for that not to be allowed on the agenda.

“But, even if it isn’t allowed on the agenda, it doesn’t change the reality that what’s happening at the ports we believe to be unlawful, that it requires Executive approval for that to continue, and Edwin Poots will take action in respect of that.

“We believe that the checks that are taking place are unlawful. That’s why Edwin Poots has to bring forward a paper if they’re to continue to operate.

“If the Executive decided by a majority that they should continue to operate, that will be a decision for other Executive colleagues to defend.

“But we believe that there is a sound legal basis for the actions that Edwin is now taking and he’ll see those through.”

Justice Minister Naomi Long backed Ms O’Neill’s legal interpretation of the issue.

“Edwin tried this before last year, he came to the Executive and tried to stop the checks,” she said.

“He got a rather clear letter from George Eustice, who was then the (UK) Defra minister, telling him that he had a legal obligation to implement them.

“And it was clear from the Executive that the status quo is that the minister must implement the checks, so Edwin would have to come and ask not to (implement them) and that is not what he’s planning to do.

“He doesn’t need us to affirm the current status quo – it is that he will do the checks.

“He would have to come and ask us not to. He will not get that permission, because I will not support Executive colleagues breaking the law.”