The Isle of Inishmore has been in Pembroke Dock since Thursday

Officials from Ireland's Labour Relations Commission met directors of Irish Ferries on Monday, before holding separate talks with union leaders.

Crews on the ships are protesting at plans to replace staff with cheaper workers from abroad.

The company said it had to bring in foreign staff to remain competitive.

Taoiseach Bertie Ahern has criticised Irish Ferries' handling of the row.

The Isle of Inishmore, moored in Pembroke Dock, and the Ulysses, docked in Holyhead, were due to sail last week.

Around 15 crew members are believed to be barricaded on each ship.

We've only our jobs left and that's what we're trying to secure Crew member Gary Jones

Some crew members seized control of the Isle of Inishmore after new eastern European crew members boarded on Thursday.

Irish Ferries said the workers were there to familiarise themselves with the vessel and their roles.

The company said it had also placed security personnel on the ships to ensure the continued access of company staff and port officials.

Unions said the existing crew were upset by the manner of the security guards' appearance.

They claimed the men had boarded in Ireland as passengers, but had then changed into their uniforms in the toilets as the vessel approached Wales.

Crew member Gary Jones, who is on the Isle of Inishmore, told BBC Radio Wales he and his fellow workers had "nothing left".

He said: "We've given a lot of things away to Irish Ferries over the last two years. They've made savings of �3.5m by taking away conditions from us.

"We've only our jobs left and that's what we're trying to secure."

'Angry'

Irish Ferries has said it had been completely open about what it was doing over bringing in new crews as part of a cost-cutting exercise. And it said it was justified in employing security staff.

Spokesman Alf McGrath said: "The security measures were necessary because in December of last year Siptu [Services, Industrial, Professional and Technical Union] staged two strikes... and totally locked up the ship in Holyhead and would not allow regulatory agencies or any management on to the ship.

"So we have a duty and responsibility to protect our assets."

An official for maritime union Numast, Tommy Molloy, said he had been denied access to the Ulysses in Holyhead.

Mr Molloy, who is also an inspector for the International Transport Federation, said the crew members on board were "very angry" at the "erosion" of their conditions.

He added: "These are people who are employed via Ireland and the UK on terms and conditions that have been agreed to be in place until 2007.

Crew members say they are trying to secure their jobs

"The recommendation of the labour courts in Ireland is that [the terms and conditions] should stay in place and the company have chosen to ignore that."

Around 70 crew members are thought to be on board the Isle of Inishmore. Police said they were keeping a minimal presence at the port in Pembroke.

On Sunday night a third Irish Ferries ship, the MV Normandy, finally arrived in Dublin, six hours after it was due to reach Ireland.