P&O has defended its choice to fire 800 workers without notice, claiming no offences were committed, a day after it announced the "biggest ever" compensation package in maritime history.

After MPs asked for confirmation laws weren't broken earlier this week, chief executive Peter Hebblethwaite said all vessels involved were registered outside of the UK and the relevant authorities were notified.

More Dover protests over P&O Ferries sackings took place today

However, this afternoon in the House of Commons, the Prime Minister, Boris Johnson said it appeared to him that P&O Ferries had "broken the law" and the government will be taking action.

He said: "We condemn the callous behaviour of P&O. I think that it is no way to treat hard-working employees and we will not sit by."

He told the Commons that the sackings appear to be a breach of Section 194 of the Trades Union and Labour Relations act of 1992.

He was also encouraging sacked workers to take action under the 1996 Employments Rights Act.

He highlighted that both acts were passed by Conservative governments.

Meanwhile, Labour leader Sir Keir Starmer accused the prime minister of “handing £50million” to Southampton port terminal operator DP World despite the sackings.

Sir Keir said: “Since the prime minister came to office, P&O have received over £38m of government contracts and the parent company DP World is lined up for £50m of taxpayers’ money under the freeports scheme."

Mr Johnson added: "If the company is found guilty they face fines running into millions of pounds.

"In addition, we will be taking steps to protect all mariners working in UK waters and ensure that that are all paid the living wage.

“But if he is asking this government to do what Labour usually want us to do and actively pitchfork away investment around the country from overseas, then that is not what we will do,” he added.

“We will take them to court, we will defend the rights of British workers.

"What we will not do is launch a wholehearted campaign, as they want, against overseas investment because that is completely wrong and wrong for those workers."

Sir Keir reacted by saying, “DP World must be quaking in their boots”.

He added: “The prime minister says how disappointed he is in them whilst handing them £50m.”

Today a third demonstration against the P&O sackings began with speeches outside the RMT's base in Snargate Street, Dover, and was followed by a march ending with more speeches at the Dover Eastern Docks roundabout.

About 100 protesters took part today, compared with the hundreds who attended the demonstrations last Thursday - when the sackings were first announced - and Friday.

Organisers said that was expected as this march and rally had been announced at short notice. They expect a higher turnout at the next protest on Saturday.

As protesters walked along the A20 Townwall Street, they chanted: "Whose, ships, our ships," and "they say low pay, we say no way."

Police set up a rolling roadblock, as before, and drivers patiently trundled behind the marchers until the road was clear for them again.

Several passing motorists blasted their horns in support of the protesters.

RMT national secretary Darren Procter had told the crowd outside Maritime House: "What about the impact it's going to have on Dover? The seafarers do an honest days' work and spend their money in the local shops, so this is far wider than the seafarers. It's the impact it's going to have on the local economy. it's going to destroy Dover.

"How can we have a maritime strategy that doesn't put people at the forefront? Companies like P&O and DP World need to sit up and take notice. What they've done is immoral and shouldn't be able to happen. And if it happens to you it will happen to the bakers, it will happen to the Royal Mail and they'll pick off every single worker in the maritime industry and beyond."

The seafarers were supported at the protest by groups such as the Dover asylum seeker charity Samphire. Kay Marsh from the group told the marchers gathered outside the Eastern Docks: "This is a whole town problem, this is a national problem.

"We need to keep coming out onto the streets as a collective and showing our solidarity to our seafarers. and to our town and our people in our town who have been treated so badly."

It comes as the scandal-hit company announced a £36.5m compensation package which has seen 40 workers receive more than £100,000, while some are expected to get over £170,000.

Many others are set to receive less than £15,000, the company said.

In a letter to Business Secretary Kwasi Kwarteng yesterday, Mr Hebblethwaite said 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”.

He wrote that notification had been made to the relevant authorities on March 17, and that no offence had been committed regarding notifying the Secretary of State.

He said the firm was “painfully aware” of the “distress” caused to workers and their families on being sacked without warning or consultation, but added that this course of action was taken as a “last resort”.

Mr Hebblethwaite has been invited to attend an evidence session jointly held by the Commons Business, Energy and Industrial Strategy (BEIS) and Transport Committees on Thursday, which will examine what options are available to the government and the workers who have lost their jobs.

In a statement, the committee chairman Darren Jones and Huw Merriman said: “This shocking story has raised questions about UK employment law, safety practices, the support of this business through a pandemic and the redress available.

“We intend to hear from the key players about what they are going to do that means these workers are not left high and dry.”

Peter Hebblethwaite, added: “I want to say sorry to the people affected and their families for the impact it’s had on them, and also to the 2,200 people who still work for P&O and will have been asked a lot of difficult questions about this.

“Over the last week, I’ve been speaking face-to-face to seafarers and their partners. They’ve lost their jobs and there is anger and shock and I completely understand.

“We needed fundamental change to make us viable. This was an incredibly difficult decision that we wrestled with but once we knew it was the only way to save the business, we had to act.

“All other routes led to the closure of P&O Ferries.

“I wish there was another way and I’m sorry.”

It comes after around 800 staff were sacked after a shock video call last Thursday, and are reported to be replaced by foreign staff working for as little as £1.80 an hour.

The ferry giant said that 575 of the 786 seafarers affected are in discussions to progress with the severance offers.

A spokesman for P&O Ferries said: “This has been an incredibly tough decision for the business: to make this choice or face taking the company into administration.

“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.”

There has been a major backlash from the public about the decision to let loose hundreds of staff - a decision which prompted two days of protests in Dover and saw calls from MPs for a criminal prosecution to be brought forward.

It was also suggested by North Thanet MP Sir Roger Gale that P&Os Pride of Kent ship should be renamed the "Shame of Dubai", as the firm is owned by Dubai-based DP world.