Nearly 3,400 Irish exporting businesses traded exclusively with the UK in 2016, according to the Central Statistics Office (CSO).
The finding, contained in a new analysis of the Republic's trade with the UK, underscores the economy's deep exposure to Brexit.
The report suggests that some 8,600 enterprises exported goods from this State in 2016 with nearly 80 per cent exporting to the UK.
Of the near 7,000 firms that exported to the UK, half traded exclusively with the country, accounting for 16 per cent of the value of Irish exports to the UK, equating to €2.4 billion.
Overall, the Republic exported €14.8 billion of goods to the UK in 2016. The agri-food sector was the biggest exporting sector, with exports of €3.5 billion, while SMEs accounted for 60 per cent of Irish UK exports.
The CSO’s report is part of a suite of Brexit-themed data being produced by the agency ahead of the UK’s planned withdrawal from the EU next year.
The latest figures don’t take account of the services side of the Republic’s trade with the UK.
With just months to go to the UK’s planned departure from the bloc, its future trading relationship with the EU has still to be decided.
Irish goods exports to Britain, the Republic’s largest European Union trading partner, were down 7 per cent in the first six months of 2018, according to separate CSO figures.
But experts believe it is too premature to link the fall-off to Brexit or the related decline in sterling, insisting the monthly trade numbers are volatile.
While a weaker sterling, which is currently trading at just under 89p against the euro, does not help exporters here, business surveys suggest trade with the UK as a whole remains strong and “the Brexit factor” hasn’t impacted trade between the two countries yet.
The Brexit-induced weakness in sterling has, however, led to a rise in cross-Border shopping, but the potential impact on VAT receipts here has not materialised with the latest exchequer numbers showing revenue from the sales tax up in year on year terms.