DUN Laoghaire Harbour Company has been called on to reverse a decision to decommission its foghorn in a step described by local councillors as "dangerous and retrograde".
From today the foghorn warning vessels of hazards in misty conditions will no longer sound.
Dun Laoghaire Rathdown County Council passed a motion at its monthly meeting calling for it to be reinstated.
Tabling the motion, Cllr Jane Dillon Byrne (Lab) said the continued sounding of the foghorn at the east pier was important for the safety of all seafarers.
Cllr Dillon Byrne said that while many ships now had either radar or GPS, "a lot of small craft going out to Dublin Bay wouldn't have either of those items".
She said some small vessels went out up to seven times a week and the temperature changes causing fog were very common in Ireland.
"I think it is a retrograde step, and highly presumptuous to presume every small craft going out to Dublin Bay has either radar or GPS," she said. "The light will remain but I think the sound is equally valuable to people who are fogbound at sea."
The councillor said she had heard a radio interview with one sailor describing how he would have lost his life without the foghorn to guide him.
"They are still useful were those systems to fail," Cllr Barry Ward (FG) said. "It would be a dangerous, regrettable and retrograde step."