Northern Ireland’s agriculture department has refused to reveal its plans for cross-border animal and food health checks under a no-deal Brexit, on the grounds that disclosure would have a “damaging effect” on “international relations”.

Although the plans would have to be implemented in less than three weeks’ time in the event Theresa May’s departure agreement fails to pass a third vote, authorities said such a disclosure would “weaken or inhibit NI’s position in the negotiations” on Brexit.

The Department of Agriculture, Environment and Rural Affairs conceded there were public interest grounds to release information about how it would protect public and animal health in a no-deal scenario.

However, it said these were not as important as political considerations. “The arguments for and against disclosure have been weighed up and whilst the general arguments in favour of disclosure apply, the balance of the public interest is in favour of withholding the information as it would have a damaging effect on UK and international relations without a compensating benefit to the public,” Daera said in response to a freedom of information request.

Although the UK, Ireland and the EU have published hundreds of no-deal notices for other sectors and for consumers, none has yet published its no-deal plans for Northern Ireland food safety or security.

In an effort to achieve disclosure, Daera was asked to provide correspondence on no-deal planning in the past six months.

The department decided there was an exemption from the usual public interest tests, even though such plans should have been in place for some time, given the original Brexit day is just two days away.

Fears that Northern Ireland could become a smuggler’s paradise for substandard food from outside the EU were fuelled after the government revealed it would not apply checks on the Irish border for customs or tariffs.

The Northern Ireland Food and Drink Association recently cited the example of cheap meat being imported from South America legally into Dublin for onward transit to the UK.

Legally, it can be stored in a bonded warehouse and not checked, giving a window of opportunity to criminals, who could make a profit by fraudulently relabelling it as British beef and exporting it to Northern Ireland supermarkets.

A source in Northern Ireland said they believed the government’s plan was to waive all food standards checks in the event of a no-deal Brexit.

A spokesperson for Daera said an appeal could be lodged in relation to freedom of information.

“Since the UK referendum, the Northern Ireland civil service has engaged in a significant programme of work which covers a range of issues,” they said.