Five dead dolphins found off the South West coast are the latest victims of an ongoing problem.
A piece of net was found close to the still-bleeding dolphins
Environmental pressure group Greenpeace said the dead dolphins were spotted near two sets of pair trawlers off Plymouth.
The deaths are the latest in the hundreds catalogued off South West shores over the last couple of years.
MPs have called on the government to take action to stop the daily slaughter of the creatures.
Observers on the Greenpeace vessel Esperanza pinpointed the dead creatures 20 miles off the coast of Plymouth.
The dolphins displayed injuries, such as broken beaks and damaged dorsal fins and flippers, consistent with being caught in
large fishing nets, says Greenpeace.
Pair trawler crews deny they are responsible for the deaths
A piece of net was found close to the still-bleeding animals, which were spotted just after 1100 GMT on Saturday.
The bodies were recovered to be brought ashore for examination.
They appeared to have been recently killed, Greenpeace said.
Pair trawlers pulling giant fishing nets with mouths as large as two football pitches are blamed for trapping the dolphins.
Jim Portus, chief executive of the South West Fish Producers Organisation, said South West boats were not to blame and that the trawlers operated out of Scotland and France.
Last year, 270 dolphins were washed ashore in Devon and Cornwall, a
figure conservationists estimated was 5% of the numbers which died in
Observers from the Whale and Dolphin Conservation Society (WDCS), on board the Esperanza, recently spotted over 1,000 dolphins off the South West coast in an area where pair trawlers are known to operate.
According to a recent report by the WDCS for Greenpeace, these pair trawlers are killing thousands of dolphins every year - hundreds of which are washed up on British and French beaches.
Greenpeace oceans campaigner Sarah Duthie said: "Around 10,000 dolphins and porpoises are killed in fishing nets every year in these waters.
"And the injuries sustained by those found this weekend could indicate that they are part of these huge and unnecessary killings.
"Unless the government takes urgent measures to stop the damage inflicted by destructive fishing practices, dolphins and porpoises could be wiped out from waters around the UK."
WDCS director of science, Mark Simmonds said: "It is high time that
this carnage ended. We call on all the relevant governments to act urgently."
The unintentional capture in fishing nets of dolphins, porpoises and other marine species is recognised to be a major problem worldwide.
It is estimated to kill some 300,000 whales, dolphins and porpoises a year.
Overall it has been estimated that 23% of the global fisheries` catch is
returned, dead, to the sea.
The Commons Environmental Committee last month warned the estimated 50 dolphin and porpoise deaths daily in trawler nets was the "most significant threat" to their worldwide population.
MPs want to see fishing nets fitted with "pinger" devices to scare off the creatures, or the temporary closure of fisheries.