The shipping group P&O has said it is planning to close its Rosslare-Cherbourg route as part of a restructuring of its ferries business.
The company plans to close four of its 13 ferry routes with the worst affected services being between England and France.
Some 1,200 jobs will be lost, and the number of ships P&O operates will be reduced from 31 to 23.
P&O said it hoped the restructuring would be largely in place by the middle of next year, but says the proposals are subject to consultation with employees.
The company operates three other Irish Sea routes, from Dublin to Liverpool and from Larne to Cairnryan and Troon.
A spokesperson for P&O Irish Sea Ferries said very few Irish jobs will be lost.
Iarnród Éireann says the impact on their workers will be mininmal but it will result in revenue loss. 90 Iarnród Éireann dock workers work in Rosslare Europort.
