The UK is pressing the EU for action to stop overfishing of the bluefin tuna, which campaigners say is being fuelled by the demand for sushi.
Britain gets through 600 tonnes of sushi a year
The environment group WWF says many EU fishing fleets are breaking the law and catching far more tuna than allowed.
Traditionally much of the catch is exported to Japan, but there is an ever-growing sushi market in Europe.
The UK government wants seasonal closure of fishing grounds and stricter rules governing tuna farms.
Demand is currently so strong that single fish can sell for thousands of pounds. With sushi continuing to be a fashionable cuisine, the UK is consuming 600 tonnes a year.
The EU has already recognised illegal industrial overfishing is going on in the Mediterranean but says there is not yet sufficient regulation or monitoring to stop it, particularly on fish farms.
Traditional fishermen who have caught bluefin tuna sustainably since Roman times now say their catches are down by 80%.
Officials from the UK's Department for Environment, Food and Rural Affairs are now pressing for urgent action.