Ferries between mainland France and Corsica and north Africa are to be hit by a strike at the height of the summer season as unions accuse the SNCM company's the government and new majority owners of breaking their word and ditching a rescue plan.
Unions have issued a call to strike from 6.00am on 24 June and say they are ready to prolong the action indefinitely.
The strike will be the third this year in a dispute that has dragged on for 17 months and could see the company close down.
The SNCM carries cars and passengers to Corsica, a popular Mediterranean holiday destination in the summer, and to north African countries, such as Algeria, Tunisia and Morocco, which are the countries of origin of many immigrants to France.
But, with cumulative losses of 250 million euros, it has serious financial problems, which have been made worse by an European Commission order to pay back 440 million euros of state aid.
The strike date was picked to coincide with the annual shareholders' meeting, which was set to hand effective control of the business to Transdev, a private transport company that owns 66 per cent of the business.
The meeting has been put off to 3 July but the strike has not been postponed, the unions saying that they hope that it can lead to a rapid settlement.
Unions accuse the government, which holds 25 per cent of the company's shares, of backing out on a rescue plan started by the previous management, which involved the purchase of four new ferries in exchange for the loss of 500 jobs out of 2,600.
Although the redundancies have begun Transdev has prevented the command for new boats, claiming that the repayment of funds to the state and the company's performance have made it unviable.
France's transport system has faced major disruption this year so far with a 10-day rail strike drawing to a close and an air traffic controllers' strike due to start.