Anger at P&O Ferries is growing after the firm sacked 800 staff without giving them any notice.
Protests are planned today at the ports of Dover, Liverpool and Hull.
The RMT union called the move by P&O as one of the "most shameful acts in the history of British industrial relations".
The UK Government is to review its contracts with P&O after it fired the employees - and plans to replace them with cheaper agency workers.
The BBC says a chorus of cross-party MPs described P&O's actions as "callous", "disgraceful" and "dastardly".
P&O sparked outrage on Thursday when it sacked nearly a quarter of its staff via a video message, telling workers it was their "final day of employment".
Nathan Donaldson, an employment solicitor at Keystone Law, commented: "The approach adopted by P&O is not unheard of, but it is exceptional to forego appropriate notice and consultation processes."
He added that a Government review of firing and rehiring in November 2021 did not outlaw the practice, but emphasised "that it should be a process of last resort".
Maritime Minister Robert Courts said he was "frankly angry at the way workers have been treated" which he told the House of Commons was "wholly unacceptable".
"Reports of workers being given zero notice and escorted off their ships with immediate effect while being told cheaper alternatives would take up their roles shows the insensitive nature by which P&O approached this issue," he said.
He added that he did not expect critical goods and services to be hit by the sudden drop in capacity, but travellers "should expect some disruption over the coming days".
Mr Courts said the company had told him it will be suspending services for "a week to 10 days while they locate new crew" on the Dover to Calais, Larne to Cairnryan, Dublin to Liverpool and Hull to Rotterdam routes.
P&O Ferries told the BBC the decision to lay-off 800 workers was "tough" but it would not be a viable business without "making swift and significant changes now".
It added: "We have made a £100million loss year-on-year, which has been covered by our parent DP World. This is not sustainable. Without these changes there is no future for P&O Ferries."
P&O Ferries is one of the UK's leading ferry companies, carrying more than 10million passengers a year before the pandemic and about 15% of all freight cargo in and out of the UK.
However, like many transport operators it saw demand slump in the pandemic.
P&O is owned by DP World, the multi-national ports and logistics company based in Dubai.