Around 200 protestors marched through Dover this afternoon, holding banners and signs as they called for P&O to reverse its decision to sack 800 staff.
Former employees were among those who attended the protest, which was organised by the RMT Union.
Protesters could be heard chanting 'Seize their ships' as they marched.
Labour MP and former Shadow Chancellor, John McDonnell, could be seen chanting with protestors.
Conservative MP, Natalie Elphicke, was also in attendance.
WATCH: ITV Meridian's Joe Coshan was live in Dover.
The Dover and Deal MP said the news was 'devastating'. She's calling for the gap in seafaring legislation to be closed to protect British jobs.
Downing Street has warned P&O Ferries it is “looking very closely” at the legality of its decision to sack 800 seafarers.
The staff were fired without notice on Thursday and replaced with cheaper agency workers.
P&O said it was left no choice but to make the 'very difficult but necessary decision'.
WATCH: Natalie Elphicke is heckled by protesters. Credit: BPM Media.
One protestor told ITV Meridian that his son, who worked for P&O, was due to get a mortgage and put an offer in on a house yesterday.
Andy, who didn't want his last name to be published, said it is a 'devastating situation' for his family.
"They were going to move on with their lives... but they're now on hold and they can't go any further with their plans
"It is just devastating news for them", he said.
WATCH: Andy tells ITV Meridian what impact P&O's actions had on his family.
The Prime Minister’s official spokesman said the Government was looking to see if P&O has broken rules.
“We are looking very closely at the actions that this company has taken to see whether they acted within the rules,” the spokesman said.
“Once we have concluded that, we will decide what the ramifications are.
“Obviously there are a lot of valid questions in relation to existing contracts.”
He said companies should only make “extreme decisions to secure the future of their business if all other avenues have failed”, adding: “We don’t believe this was the case for P&O staff but we are looking into this very carefully.”
However Labour say the government needs to be doing more, now.
Louise Haigh, MP for Sheffield, Heeley, and Shadow Secretary of State for Transport said P&O cannot treat workers in this way and the government needs to sanction the company.
Speaking to ITV Meridian in Dover, she said:
"The anger here today is reflecting across the country at the utterly disgusting behaviour of P&O Ferries.
"This Dubai based company cannot come to this country and treat workers in this way, and we are all standing in solidarity today with the P&O workers across this country."
"We've heard a lot of angry words from the government, it is not good enough. They need to step in and take action.
"They need to withdraw every single penny of public money that P&O Ferries have had, including support during the pandemic. Take sanctions against them, because if they haven't broken the law it should be illegal.
"On Monday we will be forcing a vote in parliament to make sure this is illegal in future."
WATCH: Louise Haigh, MP for Sheffield, Heeley, and Shadow Secretary of State for Transport
A spokesperson for P&O Ferries said: "We know that for our staff this redundancy came without warning or prior consultation, and we fully understand that this has caused distress for them and their families. “We took this difficult decision as a last resort and only after full consideration of all other options but, ultimately, we concluded that the business wouldn’t survive without fundamentally changed crewing arrangements, which in turn would inevitably result in redundancies.
“We also took the view, in good faith, that reaching agreement on the way forward would be impossible and against this background, that the process itself would be highly disruptive, not just for the business but for UK trade and tourism.
“We have offered enhanced severance terms to those affected to properly and promptly compensate them for the lack of warning and consultation.
"The changes we've made bring us into line with standard industry practice."
"All affected crew who were working yesterday were notified face-to-face and in-person on board their vessels.
“For crew who were off, P&O Ferries made all efforts to notify them personally: they were individually called on the phone, as well as via email and text.
“Virtual meetings were also held but only 261 of our 800 affected staff were on those calls.
“To try to minimise disruption for our customers, we contacted everyone we could reach.
“If any passengers have any queries about travelling with us, we encourage them to get in touch with our customer services team.
“Our aim is to have the first of our services running again in the next day or two as we lose £1m a day for each day they are not moving.
“The teams escorting the seafarers off our vessels were totally professional in handling this difficult task with all appropriate sensitivity.
“Contrary to rumours, none of our people wore balaclavas nor were they directed to use handcuffs nor force.”