Ferry operator Stena Line today cast doubt on the future of its Dún Laoghaire to Holyhead route.
In a statement today, the company said that the level of harbour dues being charged by Dún Laoghaire Port were a threat to the long term viability of the route.
The company warned the route may be discontinued when the current contract with Dún Laoghaire Harbour Company expires in 2011.
It warned that if the issue cannot be resolved the company would consider an expansion of its services into Dublin where port charges are considerably less than those at Dún Laoghaire. Stena Line is the only commercial operator using Dún Laoghaire Port.
A spokesman for Dún Laoghaire Harbour Company told ireland.com that the two parties had reached an agreement in 2006 whcih would run until 2011.
"At that time we agreed to reduce the fees being paid by Stena Line by 30 per cent per year."
The pspokesman went on to say that the Harbour Company "look forward to re-negotiating a new agreement" closer to 2011.
"Nearer to 2011 any agreement we come to will reflect the cost realities for teh Harbour Comapny and Stena Line," he added.
Fiona O'Malley, Progressive Democrats TD, said: "It is vital to Dún Laoghaire that Stena stays. Both companies need to work on an agreement so that consumer choice and competition are not diluted.
"A balance needs to be struck between keeping Stena competitive and developing the harbour facilities."