P&O is already wrangling with a “sky high” insurance bill, the Telegraph revealed this week, with analysis suggesting that its safety performance will be deemed “very low”. P&O was previously a “medium” rating before axing the 800 employees.

In March, P&O said that safety is “our foremost priority”. Suggestions that safety is being compromised are “categorically false”, the operator added.

It follows weeks of protests at ports by unions pushing for the company to reverse its decision over the mass sacking in the middle of March, which came without a consultation.

P&O has been struggling to resume its services since it took that decision. It had been expecting to restart sailings between Dover and Calais over the Easter weekend, but had to pull those plans.

Two of its ships on that route have been detained by the Maritime and Coastguard Agency over safety concerns. The latest, which came last week, was “due to surveyors identifying a number of deficiencies”, the agency said.

P&O has argued that the MCA is inspecting the vessels with “an unprecedented level of rigour”.

Keeping the services suspended added to travel chaos over the weekend, with thousands of travellers forced to scramble to book with rival operators.