P&O's ferry services out of Hull could undergo a radical change.
Services from Hull may be re-flagged
Sources within P&O's ferry services have said the company are considering re-flagging the Pride of Hull with a Dutch flag.
The BBC has also learned of proposals to transfer two ships from Hull to Portsmouth to work a route to France.
It means the company, who have confirmed a restructuring exercise is under way, could employ more foreign employees at cheaper rates.
Although P&O Ferries have said there are no definite plans to change any services out of Hull, union leaders are worried the move could have implications for British crew.
Steve Todd, from the Rail Maritime Transport Union, said they are working to safeguard jobs in Hull: "It is again about tax incentives and we will be a seeking reassurances regarding the jobs."