P&O Ferries workers were hauled off ships by men in balaclavas as the company made 800 staff redundant, an MP has claimed.
The ferry staff lost their jobs as P&O slashed its workforce by video message.
A P&O spokesperson said the firm needed to lay off workers due to losing £100million year on year.
All staff on board P&O ferries were ordered to leave, some with just five minutes' notice.
But the crew of the P&O vessel Pride of Hull are refusing to leave out of protest.
Labour MP Diana Johnson told the Commons today: "I understand from the RMT union [the National Union of Rail, Maritime and Transport Workers] that these agency staff, mainly from overseas, are in buses on the quayside with a security firm... wearing balaclavas and taking British crew off these ship.
Are you a worker or passenger affected by the P&O crisis? get in touch: sam.barker@mirror.co.uk
She added: "This is shameful and it goes against all norms of fair and reasonable behaviour and it's clear that foreign ratings will be employed on terms that are less favourable than our current UK seafarers are.
"And this is about a race to the bottom in terms and conditions reminiscent of the worst Thatcherite policies."
General secretary Mick Lynch of the RMT union said: "We are receiving reports that security guards at Dover are seeking to board ships with handcuffs to remove crew so they can be replaced with cheaper labour.
"We are seeking urgent legal action and are again calling for the government to take action to stop what is fast turning into one of the most shameful acts in the history of British industrial relations.
"If this happens at P&O it can happen anywhere and we are calling for mass trade union and wider public mobilisation and protest against the company."
The Pride of Hull normally sails a P&O route from Hull to Rotterdam.
East Hull MP Karl Turner said on Twitter :"I’m hearing that the captain of the Pride of Hull will refuse to allow the police to board the vessel if @POferries ask them to do so."
A sit-in was called for earlier today by the RMT.
RMT general secretary Mick Lynch, said: "We have instructed our members to remain onboard and are demanding our members across P&O's UK operations are protected, and that the Secretary of State intervenes to save UK seafarers from the dole queue."
Dozens of other P&O staff have been blocking a port road in Dover out of protest.
The affected staff held banners and flags saying "Stop the P&O jobs carve-up".
The staff began protesting after buses carrying agency workers hired to replace them arrived at the Kent port.
One of the protesters, who had worked for P&O for decades, told the PA news agency: "I refuse to move from this road. All this service for nothing.
"The police will have to take me away."
Demonstrators then began chanting "Support local jobs" before moving to another road.
A 54-year-old man, who has worked in the engine rooms of ferries since the 1980s, said: "I'm fuming, to be honest with you. I've known people who've been with the firm for years - this is no way to treat people."
P&O employs 3,000 workers and has 20 ships.
A P&O spokesperson said the firm had to lay off staff as otherwise it would not be a "viable business".
They added: "Our survival is dependent on making swift and significant changes now. Without these changes there is no future for P&O Ferries.
"These circumstances have resulted in a very difficult but necessary decision, which was only taken after seriously considering all the available options.
"As part of the process we are starting today, we are providing 800 seafarers with immediate severance notices and will be compensating them for this lack of advance notice with enhanced compensation packages. "
