French fishermen have blocked the ports of Calais and Boulogne in protest at so-called pulse fishing, which uses electrified nets to stun fish, reports BBC News.
Fishing boats stopped ferries entering or leaving Calais while a roadblock stopped traffic at Boulogne.
Calais is a major link between the UK and France used by thousands of tourists and lorries every day.
The European Parliament recently voted to ban pulse fishing which is mainly used by Dutch trawlers.
The head of P&O Ferries, Janette Bell, said the blockade of Calais was "utterly unacceptable".
"We call on the French authorities to ensure that the blockade is cleared without further delay and that Calais reopens for business," she said in a statement.
A Calais port spokeswoman said they were in talks with the fishermen. A source at the port authority later said fishermen were allowing one ferry through towards England every hour, but gave no further information.
The English port of Dover was also hit by the action, with P&O and DFDS Seaways suspending some scheduled services.
DFDS later rerouted some services through Dunkirk while P&O advised some customers to use the Channel Tunnel.
Fishermen in Boulogne set pallets and tyres alight on an access road while two French boats blockaded an area of the port where Dutch trawlers unload their catches.
Dover MP Charlie Elphicke called on French President Emmanuel Macron to "get a grip of the situation" and put a stop to the disruption which he said was damaging both the French and British economies.
Stéphane Pinto, vice president of the regional fisheries committee, said a small flotilla of boats had sailed to Calais from Boulogne and other boats from Dunkirk had joined them.
He said the fishermen faced financial losses because of the use of pulse fishing.
"We're at our wits ends. We feel abandoned," he added.
The controversial technique involves trawlers using nets that generate an electric current, stunning the fish and making them float upwards where they are easier to catch.