The company is only operating one vessel, Spirit of Britain, which was due to depart at 16.05 from Dover, the BBC said.
The ship has been back in operation for less than a week carrying freight traffic, after it was cleared to sail by safety inspectors.
P&O has still to bring back three other vessels that ply the Dover route, but these must also clear safety inspections to ensure agency crews paid an average £5.50 per hour are competent to sail them.
Passenger services have already resumed on P&O’s other routes between Liverpool and Dublin, Cairnryan and Larne and Hull to Rotterdam.
