Irish Ferries says it is unlikely to operate a service in 2019 between Rosslare and France.
The company informed customers on social media today.
"Irish Ferries wish to inform our customers that we're unlikely to operate a service between Rosslare & France in 2019. We continue to keep this situation under review."
It added the new WB Yeats ship will operate from Dublin to Cherbourg.
In response to customers, the company said the move was based on customer feedback.
"Feedback from our customers suggests that it is easier to travel to Dublin Port for most people than it is to get to Rosslare," it said.
The company will continue to run a passenger service between Rosslare and Pembroke year round.
Fianna Fáil Spokesperson on Transport, Robert Troy TD, called the announcement "bewildering".
"Increasing capacity at Rosslare Europort should have been the priority for improving connectivity with our European neighbours," he said.
"As the shortest sea route for goods and passengers to continental Europe, the Irish Ferries service was once a very popular and well-utilised service. I would like to know why efforts are not being made to restore it to its former glory.
"The withdrawal of this service represents a significant blow to Rosslare Europort. I have written to the CEO of Irish Ferries and asked him to explain the decision. I would implore him to revisit it in light of the increasingly likely ‘no-deal’ Brexit scenario."