Greenpeace protesters have found three dead dolphins with their stomachs cut open in the sea off the South West.
The dolphins were spotted by Greenpeace activists. Picture: Greenpeace/Davison
Campaigners say the animals' stomachs are likely to have been slit by fishermen in an effort to make them sink out of sight.
Protesters on the Greenpeace ship, Esperanza, are targeting bass pair trawlers which they blame for thousands of cetacean deaths every year.
Greenpeace is calling for an emergency closure of the bass fishery.
The dolphins were found in the sea on Tuesday, said Greenpeace, after volunteers in inflatable boats disrupted pair trawlers about 40 miles south of Plymouth.
Greenpeace blame pair trawlers' fishing nets, which are slung between two boats, for snaring dolphins, although fishermen deny this.
Sarah Duthie, head of Greenpeace's oceans campaign, said: "Pair trawlers kill thousands of dolphins every year, independent observers onboard trawlers have said so, and the net damaged dolphin carcasses washing up on beaches tell us the same tale.
"We need action now from fisheries minister Ben Bradshaw. He's got the power to stop dolphins dying a brutal death in these nets and he should use it now."
Greenpeace has also launched a legal challenge arguing that under the EU Habitats Directive, the UK Government is obliged to take swift and effective action to protect the dolphin population.
Last July Mr Bradshaw called for an emergency closure of the bass fisheries, but this was rejected by France and the European Fisheries Commissioner.
Mr Bradshaw on Monday won a commitment from EU fisheries ministers for a review of the data on by catch of small cetaceans in the English Channel and western approaches.
A Government-funded study found 169 dolphins were killed as by-catch in the bass fishing season from November 2003 to April 2004 - up from 30 in 2002-03.
Last year the EU agreed to undertake a series of measures including, observer schemes for fisheries suspected of dolphin and porpoise bycatch and the use of pingers (acoustic devices) to deter porpoises from fishing nets.
But the EU legislation was not due to be reviewed until 2007/8 and under Monday's agreement, all the data collected under the EU regulation and other national and EU research projects will be reviewed this year in order to determine whether further action is needed.