Ferry company bosses have written to the French Prime Minister calling for action to be taken against fishermen if they blockade the French ports again.
It follows the latest two-day blockade when ferry sailings from Dover to Calais and Boulogne were halted, leading to traffic chaos on the approaches to Dover.
Alain Vedel, P&O Ferries' port manager at Calais, sent the letter to Prime Minister Francois Fillon stressing the company's importance to the economy of Calais port and town.
"P&O Ferries has been in Calais for many years and employs more than 3000 people," said M Vedel.
"We deliberately chose this French port for our investment and our marketing effort. As such, we consider ourselves important to the port and town of Calais and to the Nord-Pas-de-Calais region.
"However, the Port of Calais is the target of recurrent blockades which impede our activity, in conflicts which originate elsewhere and with which we are not concerned. Our customers and staff are regularly made hostage to people and organisations which appear uninterested by the common good.
"Our economic interests, our reputation, the image of Calais and more generally of France, suffer from these events. Our customers are mainly British and these restrictions to the freedom of movement between E.U. member states are a brake to their desire to use our routes or even to travel in France.
"The latest example of such a blockade happened without warning and was imposed for two days by the fishermen of the French channel coast, who acted without fear of the consequences as they believe themselves untouchable.
"Whilst the Courts are prompt on each occasion to find in our favour, we cannot say the same of the State when we request its assistance to enforce such Court orders and to impose public order.
"The State, otherwise so quick to invoke public order, appears not to want to protect our business and that of the other enterprises of the Region, which suffer an undoubted prejudice.
"We therefore request that you give us your public assurance that such incidents will no longer be tolerated and that the State will grant to the private sector, which is currently so badly affected, a guarantee of labour harmony and public order which we feel entitled to demand in order to avoid being the economy’s next victim."