Dolphins could be wiped out in South West waters within four years unless the EU takes action, conservationists have warned.
Conservationists say dolphin sightings are down
A report found strandings were up and sightings were down over the last 15 years and blamed this on dolphins being caught in nets slung between trawlers.
In 2004, the practice of "pair trawling" was banned for British trawlers within 12 miles of the UK coast.
But other European boats can continue because they are outside the rules.
Dr Lissa Goodwin, from the dolphin protection charity Marine Connection, said sightings of bottlenose dolphins in the region were at an all-time low, with just 16 reported so far this year.
Sightings peaked at 335 in 1992 but by 2004 the number had fallen to just 60, she added.
''We could be having a severe impact on a sub-population of common dolphins that we could be close to wiping out,'' said Dr Goodwin.
''There is also a very real danger that we could be seeing the last of the bottlenose dolphins off the South West (Devon, Cornwall and Dorset) shores."
Numbers of dolphin strandings have risen in Devon and Cornwall
She said entanglement in fishing gear, or "bycatch", was the number one cause of death in stranded dolphins, particularly common dolphins.
Dr Goodwin said the number of strandings in the South West had risen from 58 in 1990 to more than 100 every year since 1997. Last year, there were 128 across Devon and Cornwall.
Campaigners say only an EU-wide ban on pair trawlers, and the deployment of "pinger" devices which emit a noise to warn creatures away from the nets, will save the dolphin population.
Rob Deaville of the Zoological Society of London (ZSL), which conducts post-mortems on stranded dolphins, confirmed entanglement in fishing gear was the main cause of death of dolphins in the South West over the past 15 years.
He said: "It is a particular problem in the South West, but it is likely to be a European-wide problem and needs a European-wide solution."