A P&O ferry has been detained in Larne, Northern Ireland, according to the Maritime and Coastguard Agency.
The agency said the ship, the European Causeway, was held “due to failures on crew familiarisation, vessel documentation and crew training”.
In a statement it said: “The vessel will remain under detention until all these issues are resolved by P&O Ferries.
“Only then will it be reinspected.”
The statement added: “Detention of ships is based on concerns over their safety and to prevent them going to sea.”
Transport Secretary Grant Shapps tweeted: “Following my instruction to inspect all P&O vessels prior to entering back into service, the Maritime and Coastguard Agency has detained a ship for being unfit to sail.
“I will not compromise the safety of these vessels and P&O will not be able to rush inexperienced crew through training.”
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Mr Shapps had previously called on P&O Ferries’ chief executive Peter Hebblethwaite to quit over the sacking of almost 800 workers without notice.
The company replaced its crews with cheaper agency workers last week.
The chief executive admitted the new crews are being paid below the UK’s minimum wage – apart from those on domestic routes.