A last-ditch attempt to resolve the dispute at Irish Ferries began last night after the company delivered an ultimatum to seafarers.
The talks at the Labour Relations Commission ended just after 11 and will resume at 9.30 this morning.
The company told the seafarers, who have effectively been on strike for three weeks, that its three Irish Sea vessels must be returned to service by tonight or staff will lose a substantial portion of a redundancy package on offer since September.
It also threatened to take one of the ships, the Jonathan Swift, out of service for all but the summer months and to make "immediate lay-offs" as a result. The ship sails between Dublin and Holyhead.
The threats are likely to bring to a head the bitter stand-off over the company's plan to replace up to 543 unionised seafarers with cheaper migrant labour.
Management and unions met the Labour Relations Commission last night for separate discussions.
However, Siptu marine branch organiser Paul Smyth said the union was not prepared to allow the ships to sail pending the outcome of any discussions.
Ships officers, who are members of Siptu, have refused to sail the vessels since November 24th, when security personnel, disguised as passengers, boarded two ships to begin implementation of the company's outsourcing plan.
They were followed on board the two ships, the Isle of Inishmore and the Ulysses, by agency workers who are due to replace existing staff.
In September, the staff had been given two weeks to accept a redundancy offer of eight weeks pay per year of service. Alternatively, they could keep their jobs but on reduced pay and altered conditions.
Two of the eight weeks of redundancy payments were described by the company as "goodwill" payments, conditional on staff co-operating with the changeover to agency crews.
In a notice to staff yesterday, the company's chief executive, Eamonn Rothwell, said the "goodwill" element of the package would be withdrawn unless all three Irish Sea ships were sailing by tonight.
He said management had been forced to adopt this stance because of the financial implications of the dispute. In a statement to the Stock Exchange yesterday, Irish Continental Group, which owns Irish Ferries, said the dispute had cost it €5.5 million to date.
Mr Rothwell claimed it was clear that Siptu was not interested in negotiating a settlement, "despite the company being prepared to consider conceding, among other things, the national minimum wage for future contract crews".
It was "very apparent", he said, that Siptu's main concern was pay for new staff and its desire for the "exclusive right" to represent them, rather than the right of existing staff to accept redundancy.
Siptu denied the claims, saying Irish Ferries had not made "a single offer" in talks last week at the LRC and had not indicated any willingness to pay the minimum wage.
It also denied the union had sought exclusive negotiating rights for staff who would be replacing the existing crews.
The union said it had not sought to compromise the right of any employee to avail of the redundancy offer, and claimed it was the company that "clearly has no interest in discussions".
Mr Smyth said the union had offered savings that matched the €15 million a year sought by the company in its outsourcing plan.
Last night the Seamen's Union of Ireland (SUI) repeated its call for management and Siptu to move towards a resolution of the dispute.
SUI general secretary Robert Carrick said he was consulting members about the latest development. The vast majority of SUI members had applied for redundancy, but Mr Carrick said many did so only because "a gun was put to their head". The maximum amount due to be received by an SUI member was €220,000, he said, although most would receive far smaller amounts.