A number of P&O Ferries agency staff have been fired for drinking on the job.
Seven members of the new group of workers were relieved of their duties after breaching guidelines on alcohol consumption.
The staff were controversially drafted in to replace the nearly 800 seafarers who were made redundant last month, with the ferry firm claiming its business was at risk of collapsing without the move.
They were brought in to work at cheaper rates, but the firm's ships still haven't moved from Dover port after two of them failed safety inspections - one of them twice.
Now, the company have confirmed that seven staff were found to have come back on board from shore leave while drunk.
A spokesperson for P&O Ferries said: “We can confirm that seven agency-employed seafarers who returned from shore were found to be in breach of our strict guidelines on alcohol consumption and have been dismissed with immediate effect.
"The safety of our passengers and crew is our foremost priority and we continue to operate a zero tolerance policy towards drinking whilst on duty."
Watch: Protestors take to the streets in Dover
The news comes as protestors once again took to the streets in Dover today to protest against P&O Ferries.
The demonstration started at the RMT (Rail, Maritime and Transport) union headquarters in Snargate Street and continued down towards the port and back again.
Traffic followed them in a rolling roadblock.
As they marched they chanted slogans such as “sack the board” and “they say low pay we say no way.”
Several passing drivers blasted their horns in support.
Darren Procter, National Secretary of RMT, said: “I hope P&O and DP World recognise they have made an absolute mess of this.”
Referring to the ship detentions by the Maritime and Coastguard Agency (MCA), he said: “Safety cannot be compromised and we want a decent operator to take over from P&O.”
The protest on Tuesday came to a close outside Maritime House.
Rob Williams of the National Union of Shop Stewards, said: “Who knew that they would sack trained crews? We can’t afford the likes of P&O.
“If you don’t own it you can’t control it so P&O should be nationalised and taken to public ownership.”
The second guest speaker was Ed Baldwin of the communications union CWUU. He said: ”We are here to offer solidarity with the RMT. We need solidarity with each other.”
Mr Procter said at the end of the protest: “This port is pivotal to the community and local economy. Seafarers spend their money in the local shops. The RMT and other unions supporting us in the UK and internationally are not going to go away.”
He warned that workers in other industries could suffer similar fates if P&O is allowed to “get away with it.”
He said: “The bubble of isolation that it won’t happen to me is no longer there.”