Union leaders will demand the reinstatement of sacked seafarers during talks with P&O Ferries on Friday.
The Rail, Maritime and Transport union (RMT) said it will be meeting with the company following public outcry over the dismissal of almost 800 workers last week.
The ferry operator, which was bought by Dubai-based logistics giant DP World in 2019, replaced the sacked staff with cheaper agency workers.
RMT general secretary Mick Lynch said: “RMT will be holding talks with P&O today to demand the reinstatement of our sacked seafarers.
“We welcome the massive public and political support for our campaign.
“P&O Ferries need to change course and reinstate these loyal key workers.”
On Thursday, P&O’s chief executive Peter Hebblethwaite admitted to MPs that employment law had been broken when the firm sacked the workers without notice.
Explaining the decision not to consult with trade unions, Mr Hebblethwaite told a joint session of the Commons’ transport and business select committees: “We assessed that given the fundamental nature of change, no union could accept it and therefore we chose not to consult because a consultation process would have been a sham.
“We didn’t want to put anybody through that.
“We are compensating people in full and upfront for that decision.”
Mr Hebblethwaite claimed the business would have folded had the sackings not been made.
He also stated that UK transport secretary Grant Shapps knew about the intention to cut jobs in November last year, although that was strongly denied by the Department for Transport (DfT).
On Friday, Shapps called on Mr Hebblethwaite to quit.
He told Sky News: “I thought what the boss of P&O said yesterday about knowingly breaking the law was brazen and breathtaking, and showed incredible arrogance.
“I cannot believe that he can stay in that role having admitted to deliberately go out and use a loophole – well, break the law, but also use a loophole.”
Pressed on whether that meant he was calling for Mr Hebblethwaite to resign “right now”, he said: “Yes.”
Further protests are being planned throughout the weekend as unions keep up the pressure on P&O and the Government to take action.
A demonstration is scheduled to take place outside the offices of Clyde Marine Recruitment in Glasgow on Monday morning.
RMT said it is targeting P&O’s supply chain, with Clyde Marine Recruitment accused of being “responsible for recruiting the scab labour to replace some of the union members on P&O’s routes”.
Mr Lynch stated: “We are making it clear that there is nowhere to run and nowhere to hide for those who have been complicit in the P&O jobs massacre.
“We will keep the pressure on at every opportunity until we get justice for the P&O workers.
“We look forward to another good turnout on Monday and greatly appreciate the remarkable solidarity from our trade union colleagues in this dispute.”
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