Over 10,000 firms completed one million post-Brexit declarations with customs to move goods from Great Britain into Northern Ireland in 2021, the first year of operation of post-Brexit checks that London is now seeking to scrap.

Under the Northern Ireland Protocol, part of Britain's withdrawal agreement from the European Union, the North effectively remained in the EU's single market for goods, given its open border with the Republic, as the rest of the United Kingdom departed last year.

That necessitated the introduction of checks on goods moving to the North from elsewhere in the UK. The first set of annual data from Britain's tax office showed that €12.4billion worth of goods required declarations.

Legislation allowing Britain to scrap the checks is working its way through the UK parliament, in a move that would raise the risk of a trade war and a new clash between London and Brussels.

Liz Truss, the favourite to become Britain's prime minister next week, has said she is determined to deliver the bill in full.

In Association with

The move has faced strong criticism from the EU as well as Northern Irish business groups, who want the checks to be eased through negotiation and fear that unilateral action from London could erase the advantages they have also gained under the protocol.

Northern Ireland's statistics office has yet to publish data comparing how trade with mainland Britain fared in 2021 versus 2020 when no checks were required.

Trade across the border with the Republic has grown rapidly, with goods moving south from Northern Ireland up 65% last year and exports to the North 54% higher.