Indian agency workers hired to replace P&O Ferries crews in Dover are being paid £1.81 an hour, a union claims.
The Rail, Maritime and Transport union (RMT) said the low pay was a “shocking exploitation” and “a betrayal of those who have been sacked”.
P&O said the figure was inaccurate but said it could not comment on how much agencies pay workers on ferries.
Some of P&O’s ferries are registered in Cyprus, meaning they do not have to pay the minimum wage required by UK law.
Firms using UK ports often register ships in other countries, allowing them to pay lower wages.
The minimum wage in the UK for people aged 23 and above is £8.91 per hour.
Transport Secretary Grant Shapps told Parliament: “Maritime employees have not, in this country, indeed throughout much of the world, received some of the same benefits and protections that exist otherwise for workers and this simply not good enough and it’s a practice we have been seeking to end.”
He said ships in UK waters operated under international law governed by treaties, so UK law did not always apply.
“These complications allow for employers to take advantage in a way that we’ve seen I think with P&O Ferries,” Mr Shapps added.
Mr Shapps told MPs that he first found out about the prospect of P&O redundancies at 20:30 GMT the evening before the workers were being sacked, but he said it wasn’t until he was at the despatch box the next day that he was made fully aware of the scale.
Previously, officials at the Department of Transport had told the BBC that Mr Shapps and the maritime minister Robert Courts had not been informed until Thursday.
Shadow transport secretary Louise Haigh said government ministers had “completely failed to act” and the reported rates of pay were “nothing short of a betrayal of the workers who protected this country’s supply chain during the pandemic”.
A spokesman for P&O said safety was the utmost priority and the new crewing management model was used by many competitors.
“They have recruited high-quality experienced seafarers, who will now familiarise themselves with the ships, going through all mandatory training requirements set out by our regulators,” he said.
Mr Shapps said the government was reviewing all of its contracts with P&O Ferries.
He had asked the insolvency service whether P&O had followed rules for redundancies – and if they had not, “that would be a matter for criminal prosecution and unlimited fines”.
Mr Shapps also told MPs P&O Ferries should remove British references from their ships if they replace sacked workers with non-UK staff.
The Spirit of Britain, Pride of Canterbury and Pride of Hull are among the names used for the operator’s ferries.
The Transport Secretary told MPs it would be “completely inappropriate” for the company to “attach themselves to this country” without having British workers.
Protests took place close to Parliament and also outside the London offices of P&O owners, DP World on Monday.
John, a former seafarer with P&O Ferries based in Dover said the redundancies were “a catastrophe” for all crew involved and he wants the company’s chief executive to resign.
“A company who had built up its reputation over 180 years just to be trashed in one single morning of madness by those responsible.
“It’s not just a job, it’s a home and to be kicked off the ship in the most unceremonious way…it’s a catastrophe for all our lives,” John, who did not want to give his surname, added.
He expects to lose his severance pay for speaking out to media, but said he “knew the difference between right and wrong”.
RMT general secretary Mick Lynch said P&O staff were “being replaced by exploited workers, vulnerable workers from overseas”.
“We have no beef with those people. We want those people to be paid the wages that we’ve negotiated for in this country,” he said.
The union has called for a boycott of P&O services and is urging the government to look at legal options to reinstate the sacked workers.
Ferries between Liverpool and Dublin have restarted and other routes are expected to follow by the end of the week.
Services were stopped on Thursday after P&O announced in a video call that 800 staff were being sacked with immediate effect.
The M20 in Kent will close between junctions 8 and 9 from 20:00 GMT while a barrier system is put in place to manage any disruption caused by P&O freight, National Highways said.
The motorway is expected to reopen at 06:00 GMT on Tuesday when lorries heading for the Port of Dover or the Eurotunnel will use the coastbound carriageway on the M20, where it will be queued if necessary.
All other traffic – including local freight and car drivers headed for the continent – should follow the signs and cross over to enter the contraflow on the M20 London bound carriageway, National Highways said.