Cheaper agency workers hired by P&O Ferries to replace laid-off seafarers did not know how to use lifesaving devices, according to a new report.
A total of 23 breakdowns on Spirit of Britain have been discovered by UK Maritime and Coastguard Agency (MCA) inspectors.
The fast lifeboats were not properly maintained and the oil filtering equipment was not working.
There were also five deficiencies relating to working conditions and five relating to fire safety systems.
Spirit of Britain was detained following the April 11 inspection, before being cleared to sail on April 22.
The ship was used by P&O Ferries to restart operations between Dover and Calais on Tuesday for the first time since the company laid off nearly 800 seafarers and replaced them with temps on March 17 to save money.
The 23 safety failures were listed without further details by the Paris Memorandum of Understanding (MOU), which is an alliance of 27 national maritime authorities including the UK.
He said there was a “lack of familiarity” with the “operation of life-saving appliances”, which could relate to equipment such as lifeboats, lifeboats, life jackets or flares.
RMT General Secretary Mick Lynch described the report as “further evidence that P&O is a capitalist bandit sailing our waters”.
He said: “The lack of care and respect that P&O clearly has for safety rules – which are designed to save lives in the event of a maritime emergency – is on par with their appalling treatment of the 800 loyal employees who have were fired last month.
“There is no doubt that the public and shipping companies should boycott P&O Ferries on grounds of safety, security and morality until the government steps in and takes over the management of this rogue shipping operator.”
Spirit of Britain was built in 2011 and can carry up to 2,000 passengers.
At 213 meters long, it is one of the largest ferries in Europe.
Thirty-one safety flaws were discovered by the MCA on another P&O Ferries vessel, European Causeway, leading to its detention on March 25.
Analysis by the PA news agency found that was more than any of the other 46,000 port state control inspections of ships under the Paris MoU during of the last three years.
European Causeway was cleared to sail on April 8 but suffered a power outage on Tuesday which left it adrift in the Irish Sea for over an hour.
The MCA said it could sail again with a restriction on the generators it could use for electricity.
A total of eight P&O Ferries ships will be probed by the agency following the mass layoffs.
Pride of Kent remains in custody after failing an inspection, while Pride of Canterbury and Spirit of France are also out of commission as they have not been fully screened.
Pride of Hull, Norbay and European Highlander have all been cleared to resume sailing.
UK Transport Secretary Grant Shapps told the transport select committee on Wednesday that he had ordered the MCA to examine the ships “with a fine-tooth comb”.
P&O Ferries previously said the inspections were being carried out with “an unprecedented level of rigor”.
In response, the MCA said its inspectors work in “exactly the same robust way” for each vessel.
P&O Ferries pays its new crew an average of £5.50 per hour, which it says is in line with international shipping laws.
Mr Shapps announced on Thursday that legislation requiring ferry operators using UK ports to pay seafarers at least the national minimum wage of £9.50 an hour will be included in the Queen’s Speech on May 10.
P&O Ferries said it would ‘fully welcome’ moves to raise wages for all seafarers in UK waters as it wants ‘a level playing field’.
Irish Ferries, which also uses a low-cost labor model, began competing with the company on the Dover-Calais route in June 2021.