A criminal investigation has been opened into P&O Ferries following the sacking of 800 seafarers a fortnight ago.

The Insolvency Service said that it has “initiated formal criminal and civil investigations” in the actions of the ferry operator and its directors.

In a letter to Kwasi Kwarteng, the Business Secretary, officials said they had conducted a review into the events surrounding the sacking.

UK companies must notify the Government before making more than 100 workers redundant. Failure to do so can be a criminal offence.

Ministers have claimed that P&O did not “appear” to comply with these laws.

P&O has said that it notified Whitehall officials a day before the redundancies. Furthermore, it was only obliged to notify the country where its vessels are flagged. P&O “reflagged” its vessels to Cyprus and the Bahamas in 2019.

The criminal investigation comes with seven of P&O’s eight ferries moored up in ports while the Maritime & Coastguard Agency conducts safety checks. Two P&O vessels – the Pride of Kent and European Causeway – have been detained after failing the agency’s tests.

Grant Shapps, the Transport Secretary, has vowed to force P&O and other operators to pay the minimum wage of £9.50-an-hour in British waters.

However, Mr Shapps conceded that he would need the support of EU countries to ram through the changes while new legislation is debated and put in place.

He faced a backlash from port operators on Wednesday over plans for them to turn away vessels that employed staff not paying the UK minimum wage.

Richard Ballantyne, head of the British Ports Association, said Mr Shapps’ proposals were “unworkable”.

A spokesman for the Insolvency Service said: “As these are ongoing investigations, no further comment or information can be provided at this time.”