A group of angry fisherman have prevented the Greenpeace ship Rainbow Warrior II, which is campaigning for a ban on tuna fishing, docking at the southern French port of Marseilles.

The men, fearing their trade will be destroyed, circled the Rainbow warrior in 25 tuna fishing boats, stopping it from moving into Marseilles' harbour and forcing it further out to sea.

"They clearly want to make us leave," said Yannick Jadot, a Greenpeace spokesman who was monitoring the standoff from a motor launch.

"Not only are their fishing practices illegal, but also their comportment in the sea lanes," he added.

Greenpeace activists on board were seen taking photos of the opposing vessels, while three police boats were stationed nearby.

The fishermen oppose Greenpeace’s plans to campaign in Marseilles against overfishing of bluefin tuna. They deny that the fish is in danger of extinction and claim that Asian groups using Spanish dummy companies are the ones responsible for any quota breaches.

In a report published in July, Greenpeace said that illegal fishing in the Mediterranean threatened to wipe out bluefin tuna and called for an immediate ban on trawling to allow stocks to recover.

The World Wide Fund for Nature also found in a separate report that bluefin tuna were in danger of disappearing because of illegal catches by French, Turkish and Libyan boats.

Many scientists agree that the species is being overfished despite the imposition of quotas eight years ago.

"The species is being exploited in an unsustainable way," Philippe Gros, the director of the French Research Institute for Exploitation of the Sea (Ifremer), said. The increased popularity of sushi was largely to blame, he added.

Greenpeace has been travelling around the Mediterranean to promote its tuna campaign and had hoped to spend two days in Marseilles.

Local authorities decided last week to deny the Greenpeace ship access to their harbour for "security reasons", but later partially relented, granting it permission to make a brief "technical" stop in the southern Mediterranean port city.

Pierre Ramel, Greenpeace’s director of campaigns said the blockade was preventing the Rainbow Warrior II from making a an authorised brief stop in the port to fill its water tanks and obtain equipment.

The Rainbow Warrior II is the ship that replaced the original Rainbow Warrior, which was sunk by the French secret services in Auckland harbour in 1985, killing a crew member.

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