Responding to a letter from business secretary Kwasi Kwarteng, Peter Hebblethwaite said all relevant authorities were notified on 17 March – a day before the line announced it was making hundreds of its employees redundant and planned to replace them with agency workers.

The move has sparked outrage throughout travel, among unions and government, with two parliamentary select committees set to join forces on Thursday (24 March) to hold a one-off evidence session.

P&O’s bosses have been invited to attend, as have representatives from the company’s Dubai-based owner DP World. MPs also want to hear from the Insolvency Service, unions and employment law experts.

However, late on Tuesday (22 March), Hebblethwaite told Kwarteng he did not believe P&O had committed any office with regard to informing transport secretary Grant Shapps of plan to sack 786 of its seafarers.

Kwarteng said there were "clear rules" around the processes employers must follow when making large groups of staff redundant, including consulting with trade union or employee representatives and "notifying, in advance of these consultations, the secretary of state via the Insolvency Service and the Redundancy Payment Service."

"Failure to meet the notification obligation is a criminal offence and can lead to an unlimited fine," wrote Kwarteng. "We note that in this case that P&O Ferries appears to have failed to follow this process."

Hebblethwaite, though, argued back: "The very clear statutory obligation in the particular circumstances that applied was for each company to notify the competent authority of the state where the vessel is registered. All relevant vessels are registered outside of the UK. Notification was made to the relevant authorities on 17 March 2022."

Sky News, however, reports a change to the law signed off by former transport secretary Chris Grayling in 2018 meant it was no longer a requirement for companies to notify the secretary of state of any plans for mass redundancies onboard ships registered overseas.

Maritime lawyer Kevin Barnett told the broadcaster: "The amendment states the notification must be made to the competent authority of the state where the ship is registered, instead of the secretary of state."

In his letter, Hebblethwaite confirmed the majority of the 786 seafarers made redundant were working onboard eight P&O vessels – four of which are registered in Cyprus, three in the Bahamas and one in Bermuda.

The RMT union, which represents P&O Ferries seafarers, has vowed to continue to protest the move, branding P&O and DP World’s decision "a shameful act of industrial vandalism" and calling for a boycott of services operated by P&O Ferries. It has warned the situation has underlined weaknesses in UK employment law.

In a statement, P&O Ferries said the total value of its financial settlement ran to £36.5 million, and included 2.5 weeks’ uncapped salary for each year in employed, up to 13 weeks’ salary in lieu of notice, and 13 weeks’ salary on top in the absence of a consultation period. "No employee will receive less than £15,000," it said. The company added employees were being supported to fine a new job at sea or ashore.

"This has been an incredibly tough decision for the business: to make this choice or face taking the company into administration," said a P&O Ferries spokesperson. "This would have meant the loss of 3,000 jobs and the end of P&O Ferries.

"In making this hard choice, we have guaranteed the future viability of P&O Ferries, avoided large-scale and lengthy disruption, and secured Britain’s trading capacity."

Hebblethwaite added: "We did this as a last resort and only after full consideration of all other options."