Major supermarkets have warned the government that "urgent intervention" is needed to prevent significant disruption to Northern Ireland food supplies in the coming months.
Britain is no longer part of the EU's single market and customs union, but Northern Ireland has a foot in both camps – part of the UK's customs territory but also still aligned with the EU's single market for goods.
Britain and the EU agreed in December that supermarkets selling into Northern Ireland would have a three-month grace period to adapt their supply systems to the post-Brexit trading reality.
Despite that some supermarkets in Northern Ireland have had shortages of fresh goods usually imported from Britain since the turn of the year because they have struggled to shift to new processes and bureaucratic procedures.
The bosses of retailers, including Tesco, Sainsbury's, Asda and Marks & Spencer, have written to Cabinet Office minister Michael Gove, warning the situation could worsen.
In the letter, they said it was essential a long-term solution is agreed with the EU before the current grace period for simplified controls ends on March 31.
"All our businesses and suppliers have invested significantly in the last few months to avoid disruption but that will become inevitable if the proposals governing movement of food from Great Britain to Northern Ireland are adopted," it said.
"We recognise the European Commission needs to see increased compliance to support the concessions it granted through the Northern Ireland protocol but the current proposals, increased bureaucracy and certification in such a short timescale, are unworkable."
The CEOs called on Gove to create a dedicated working group to co-ordinate government agencies to integrate customs and food controls, and to use the supermarket groups' experts to develop the best solution.
And they want the government to agree with the EU that more time is required to implement a new system.
"It also requires an open discussion with the EU explaining why we can't accommodate changes to the current approach to transporting food to Northern Ireland but stressing we are working towards a robust system as quickly as possible," the letter said.
A British government spokeswoman said a new dedicated team had already been set up and would be working with supermarkets, the food industry and the Northern Ireland Executive to develop ways to streamline the movement of goods in accordance with the Protocol.
“The grace period for supermarkets and their suppliers is working well, goods continue to flow effectively between Great Britain and Northern Ireland and we are working intensively with industry as new requirements come in," she said.
