Britain's Maritime and Coastguard Agency (MCA) on Friday detained a ferry operated by P&O in Northern Ireland because it was not ready to sail, the agency and P&O said.
The British government has already said it will take legal action over P&O Ferries' decision to fire 800 staff earlier this month with immediate effect.
The ferry European Causeway, which operates between Cairnryan in Scotland and Larne in Northern Ireland, will be detained until the company resolves all the issues, a spokesperson for the MCA said, citing "crew familiarisation, vessel documentation and crew training".
