More than half of Irish Ferries staff of 1,200 had been laid off by last night as a strike by ships officers continued.
The strike by SIPTU members has caused the cancellation of all of the company's services and threatens to disrupt Irish exports to Britain.
The action is in response to the company's decision to outsource employment next year on its sailings between Rosslare and France.
The union announced yesterday that its ratings members had balloted overwhelmingly to take industrial action on the issue, following an earlier ballot in favour of a strike by ships officers.
A company spokesman said that 650 staff had been laid off by last night as a result of the dispute.
SIPTU official Mr Paul Smyth said the union was prepared to enter talks with management to agree "substantial cost savings" on the French route.
However, the company's director of human resources, Mr Alf McGrath, said the outsourcing move will save the company €3.5 million next year.
He had received no indication from SIPTU that it had alternative proposals that would achieve cost savings even close to that.
Mr Smyth called on the company to enter discussions "without preconditions". The company says it won't talk while a strike is in place.
