Staff on the Pride of Hull ship have left the vessel after refusing to leave earlier today.
They staged a protest "sit-in" on board the P&O ferry for several hours after the company made 800 workers redundant with immediate effect.
The company has suspended all services and is planning to use an agency to keep its ferries running, with current staff able to apply to the agency for work.
Karl Turner, the MP for East Hull, posted a picture on social media which he said showed the captain of the Pride of Hull addressing staff after they refused to disembark at King George Dock.
An earlier tweet showed the ferry moored at the dock, along with another picture said to show replacement workers waiting to board.
Mr Turner wrote: "New foreign crew waiting to board the Pride of Hull on King George Dock. RMT Union sitting in onboard the vessel. They will not be boarding her. We understand that both current officers and ratings are to be sacked."
Mr Turner added that the captain of the ship would "refuse to allow the police to board".
Writing on Facebook, Mr Turner said: "I stand in full solidarity with the British workers and crew across P&O, and will do all I can as an MP. We warned this could happen and the government have just stood by, it is outrageous."
The protest came before P&O Ferries released a statement on Thursday afternoon saying that it was not a "viable business".
The statement said: "We have made a £100m loss year on year, which has been covered by our parent DP World. This is not sustainable.
"Our survival is dependent on making swift and significant changes now. Without these changes there is no future for P&O Ferries."
The sit-in ended on Thursday afternoon.
But unions have reacted angrily to the company's decision.
In a statement the RMT Union said it "demands protection of UK seafarer jobs amid speculation that hundreds of UK seafarers are to be sacked and replaced with foreign labour".
General secretary Mick Lynch said: "We are deeply disturbed by growing speculation that the company are today planning to sack hundreds of UK seafarers and replace them with foreign labour.
"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."