Grant Shapps, the Transport Secretary, has called on Mr Hebblethwaite to resign and pledged to bring in new laws to force P&O to pay the minimum wage.
The Maritime and Coastguard Agency is part of the Department for Transport.
The P&O spokesman added: “For those customers still affected by wider disruption, we are providing refunds to all passengers booked to travel with us to whom we have not been able to provide alternative services. Customers can contact our customer service team by email or phone for a refund.
“Anyone who has had their trip disrupted with P&O will also receive a free trip to be used on a future journey with us, that can be taken later in the year. We thank our customers for their patience during this time and we apologise to those customers whose journeys have been cancelled and disrupted.”
Separately, a former P&O Ferries chef has launched a £76m legal battle against the company after claiming he was treated unfairly and lost his job because he was British.
John Lansdown, one of 800 seafarers who was sacked suddenly three weeks ago, is the only former employee to take action against P&O after refusing to accept a severance package.
The 39-year-old, who joined P&O as a trainee at the age of 16 and was earning £30,827 a year, is seeking up to £76m in damages after claiming unfair dismissal, racial discrimination and harassment.
He claims his nationality affected his redundancy as P&O replaced staff with non-British crew who could be paid an average of £5.50 an hour — less than the minimum wage.
He also said workers were removed by private security staff wearing balaclavas and carrying handcuffs.
A spokesman for P&O: “The decision by P&O Ferries to make seafarers redundant was categorically not based on race or the nationality of the staff involved. No staff involved in the redundancies wore balaclavas nor were they directed to use handcuffs or force.”
Mr Hebblethwaite shocked MPs earlier this month when he said that his company broke the law by sacking 800 seafarers on the spot and that he would do it again if he had to, telling an emergency Commons committee there was “absolutely no doubt” that under UK employment law the ferry operator was required to consult unions before the redundancies.
Mr Lansdown called the redundancies a “sham” in legal papers, adding that he wanted to use any money from his claim to campaign for the end of “fire and hire” practices and hoped his case would “deter” P&O from doing the same thing again in future.
His move comes days after a criminal investigation was 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.
A P&O spokesman added that the company has “offered enhanced severance terms to those affected to properly and promptly compensate them for the lack of warning and consultation – all staff offered these terms except Mr Lansdown have accepted this offer”.
“The business was losing £100m a year, and no shareholder would be able to continually finance that year on year. P&O Ferries needed fundamental change to make it viable”.
Mr Lansdown said: “The actions of P&O Ferries have upended the lives of 800 loyal and dedicated seafarers and their families. Their grotesque disregard for due process in this country will set a dangerous precedent if allowed to stand”.
