The trade union SIPTU has said it has served strike notice on Irish Ferries after the company offered voluntary redundancy packages to 543 staff earlier today.
The 543 people affected are the ferry firm's seafaring workers on its Irish Sea services on the Dublin-Holyhead and Rosslare-Pembroke routes.
A statement from the company said it could not continue its operations with current high costs in the face of increased competition from rival shipping operators and low cost airlines.
It said the situation had deteriorated this year with a 9% drop in the Irish Sea car passenger market and rises of up to 50% in the cost of fuel.
The Minister for the Marine, Pat 'The Cope' Gallagher, said he understood the commercial pressures faced in shipping but that he is disappoint by the decision of the company which creates grave consequences for Irish seafaring employment.
Irish Ferries also said it had been 'unsuccessfully negotiating' with SIPTU and the Seaman's Union of Ireland to achieve cost reductions.
The company has given workers the option of staying, but on rates of pay tabled by unions at the Labour Relations Commission in January for the retention of staff on Irish Ferries' MV Normandy.
A decision by Irish Ferries to outsource crewing on its Rosslare to France routes earlier this year led to a strike.
The redundancy package is for up to eight weeks pay per year of service, including statutory two weeks.
Irish Ferries added that this would be available provided there was agreement on the company's right to replace departing staff with crew from an agency employing EU personnel.
Chief Executive Eamonn Rothwell said he regretted having to write to staff in this way.
