Fishermen are calling for Royal Navy protection after claims they were attacked by French vessels.
Kevin Lochrane, from East Sussex, said he was surrounded by seven or eights boats in international waters 15 miles off Caen in a dispute over scallops.
One Scottish fisherman, Andy Scott, said he feared for his crew’s safety during the incident.
Other crewmen, including from Devon, said they were also surrounded by the French fishermen.
They said the French fishermen had tried to damage their gear.
’Called for assistance’
Clinton Powell, from Devon, said : "Something has got to be done and we need naval protection."
Anton Bailey, from Brixham, claimed four French boats "threw rocks and tried to ram us". Anton Bailey Anton Bailey claims four French boats "threw rocks and tried to ram us"
Mr Lochrane, from Newhaven, said he had to call his crew off the deck "as it was unsafe".
"I called other vessels for assistance and when they arrived they had ropes fired at them too, and nets and ropes were put in the water to disable us."
He said a French fishing protection vessel refused to intervene.
"I’ve been at sea for 20 years and never seen anything like it," Mr Lochrane said.
Fisheries Minister Richard Benyon said : "UK vessels have a legitimate right to fish in these waters and France must continue to provide adequate protection to UK fishermen.
"We are monitoring the situation and will continue to keep an open dialogue with our French counterparts."
The Maritime and Coastguard Agency contacted French coastguards, who sent a patrol vessel to the area and said the French authorities were "continuing to monitor the situation".
The French Government says there is nothing it can do to stop the British boats, because they are in French waters perfectly legally.
Mr Powell, who was fishing on board The Golden Fleece Two, said : "None of our skippers could get away with it : we’d be locked up and legal action taken right away."