The supply chain between Northern Ireland and the rest of the UK is a "boat breakdown" away from collapse as a result of the post-Brexit regulatory border, the UK's Road Haulage Association has warned the British government.

In a letter sent to Cabinet Office minister Michael Gove seen by Reuters, the RHA said some sectors are "struggling enormously" with the new, complex rules just over a week after the United Kingdom left the European Union's orbit.

While the UK is no longer part of the EU's single market and customs union, Northern Ireland has a foot in both camps, as it is part of the UK's customs territory but also still aligned with the EU's single market for goods.

The new rules have left some shelves empty this week as supermarkets struggle to import fresh goods from Britain and manufacturers have reported Northern Irish-bound trucks being unable to cross the Irish Sea due to difficulties with customs declarations.

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The RHA said raw material supply lines from Britain had also been restricted due to the regulatory changes and that factories had already reported serious supply chain issues, including failures to supply retail contracts.

The trade body warned Mr Gove that introducing some of the world's most complex customs processes with next to no training, implementation time and insufficient capacity left industry "one storm/Covid event/boat breakdown" away from having serious supply issues.

RHA Chief Executive Richard Burnett said in the letter: "This would result in shortages on (Northern Irish) supermarket shelves and factories being starved of materials."

Mr Burnett also cautioned that the Covid-19 lockdown that will keep Northern Ireland's hospitality sector and non-essential retailers shut for another month is "simply masking a crisis in the supply chain to food service and hospitality."

Yesterday, Mr Gove said that difficulties in moving goods between Northern Ireland and the rest of the United Kingdom will get worse before they get better.