Ferry operators have still to be told whether their vessels are subject to the smoking ban, more than two weeks after the new legislation took effect.
Stena Line said it had contacted the Office of Tobacco Control, the Department of Health and the Health and Safety Authority about the implementation of the ban more than two weeks before its introduction, but had had no response.
Unlike Irish Ferries, the Stena Line fleet is registered under the British flag but, the company said, it was unclear whether the ban would apply to its vessels operating out of Irish ports, or while the ferries were in Irish waters.
However, the Department of Health told The Irish Times last night that the company was breaking the law if it allowed smoking in the workplace within the Irish jurisdiction.
"There is total confusion as to who this applies to. We have asked for clarification and we did that a good two weeks before March 29th, but we're still waiting on an answer," a Stena Line spokesman, Mr Terry Doyle, said.
Stena has implemented the smoking ban in its offices in Dún Laoghaire and Rosslare. On its high-speed HSS service, smoking is only allowed outside on deck, but on its conventional ferries it is permitted in designated indoor areas.
Irish Ferries, whose vessels are on the Irish register, has implemented the ban on all its vessels. A spokesman for the company said it was too early to tell if the ban was having an effect of passenger numbers.
However, the company was still looking for clarification on how the smoking ban affected the crew, he said.
"What we need to know is whether staff cabins are places of residence and if they can smoke there," he said.
