Northern Ireland is facing disruptions to its food supply because suppliers in Great Britain are unaware of the Brexit-related paperwork needed to send goods to the region, business leaders have said. Trucks are arriving at GB ports with incorrect or absent documentation that delays their passage across the Irish Sea, they told MPs on Wednesday. Many operators in Great Britain seemed unaware that since 11pm on New Year’s Eve Northern Ireland was applying EU customs rules at its ports, meaning goods crossing the Irish Sea from other parts of the UK were subject to customs checks, Seamus Leheny, of the freight trade body Logistics UK, told the Northern Ireland affairs committee. “We had lorries arriving into Belfast with no documentation at all … it’s the lack of preparation on the GB side.” One large manufacturer had 15 lorries of food bound for Northern Ireland stuck because they lacked customs declarations, said Leheny. He cited another company that sent 285 lorries to Great Britain but only 100 returned, leading to knock-on disruption of supply chains. Another company resolved documentation problems after studying a YouTube tutorial. Leheny said ports and customs officials were working hard and flexibly to minimise disruption but he urged the government to improve communication so that hauliers were not left figuring out paperwork on their own. Aodhán Connolly, director of the Northern Ireland Retail Consortium, told MPs that authorities in Belfast and London needed to be “shouting from the rooftops” so that suppliers and parcel companies understood the new rules. “This is a very turbulent time where decisions need to be taken at speed,” he said. Sainsbury’s has been forced to fill some of its Northern Ireland supermarket shelves with Spar-branded products. Shoppers at Tesco and other chains have reported bare shelves in some sections, especially chilled food. England, Scotland and Wales left the European Union’s single market for goods on 31 December but Northern Ireland did not. Products containing animal parts require export health certificates in accordance with EU regulations. Ian Paisley, an MP with the Democratic Unionist party, said the special arrangements for the region had been a “disaster” and justified ditching the Northern Ireland protocol, which had cleared the way for the final Brexit deal between London and Brussels. Brandon Lewis, the Northern Ireland secretary, told BBC Radio Ulster that companies were adapting to changes. “I think people will see, as things settle down, that things will flow as they did in 2020.”