The Greenpeace volunteers entered the European Seafood Exposition in Brussels - where many UK supermarkets buy from the 1,600 exhibitors - at 10am. Using fishing nets and chains, they shut down the tuna traders' stands and used the public address system to urge industry buyers to purchase only sustainable seafood.

The campaigners are calling for a worldwide ban on the sale of threatened tuna, such as bluefin, until stocks recover. The European Seafood Exhibition is the largest event of its kind in the world and exhibitors' average sales reach millions of euros.

The five seafood suppliers shut down by Greenpeace are: Mitsubishi Corporation of Japan, the world's largest tuna trader and owner of Princes, the UK food and drink group; Spain's Ricardo Fuentes, which controls an estimated 60 per cent of Mediterranean bluefin tuna production; Dongwon Fisheries from Korea, which has a 75 per cent share of the Korean tuna market; Azzopardi Fisheries of Malta, the largest tuna farmers in the Mediterranean; and the Taiwanese Moon Marine, who are heavily involved in tuna longline fisheries in Indonesia.

Speaking from the Seafood Exposition, Willie Mackenzie of Greenpeace said: "These companies are responsible for pushing tuna towards commercial extinction. Unless urgent action is taken, overfishing and the destructive and short-sighted methods of these companies could see the end of the tuna trade, because there won't be enough left.

"Put simply, there are too many ships chasing too few fish. Designating large areas as ‘marine reserves', would allow the seas and fish stocks to recover and ensure a sustainable future for the fishing industry. Failing to do so spells disaster for conservation, disaster for fish stocks, and disaster for the long term interests of fishermen."

Worldwide, up to 90 per cent of stocks of large predatory fish - including tuna, swordfish, cod, and halibut - have already been lost.