Goods passing through Irish ports increased more than 5% last year, with Britain and the North by far the most valuable trading partner, figures have shown.
The reliance of ports in the Republic on the North and mainland Britain give credence to calls from business leaders to insulate the marine industry from the effects of Brexit.
CSO figures show routes between Dublin and Holyhead, Liverpool and Milford Haven in Britain were the busiest routes for inward movement of goods in 2017, while Dublin-Holyhead and Dublin-Liverpool routes were also the busiest routes in terms of goods forwarded.
Irish ports handled more than 53 million tonnes of goods in 2017, an increase of 5.2% when compared with 2016.
Goods forwarded from Irish ports amounted to almost 18 million tonnes in 2017, while a total of 35.5 million tonnes of goods were received in 2017, both increasing by 5.2% when compared with the previous year, the CSO said.
Calls for additional funding for Irish ports in a post-Brexit EU have gained momentum in recent months.
Port of Cork chairman John Mullins told the Oireachtas transport committee in February that Brexit was “now a real issue” for Irish imports and exports.
"If there is a hard Brexit and it leads to major queues in Holyhead or in Fishguard, this will create an enormous issue for the supply chain, he said."
Chief executive Brendan Keating warned earlier this year that the country is at significant risk of isolation following Brexit and will need EU funding to shore up lack of connectivity to major European routes.