Dolphins off the South West (Devon, Cornwall and Dorset) coast are in severe danger of being completely wiped out, marine conservationists have warned.

They say increasing numbers are being killed, after getting caught in nets slung between trawlers.

In 2004, the British government introduced a unilateral ban on pair trawling for seabass within 12 miles of the UK coast.

Other measures introduced included a licensing system for UK boats within the 12 to 200 miles zone.

However, other European vessels can continue to trawl because they are outside the rules.

Vast trawl nets the size of a football pitch are towed behind a pair of fishing boats, trapping dolphins, porpoises and even small whales.

A report by dolphin protection charity Marine Connection and The Wildlife Trusts shows that there has been a sharp decline in sightings for some species, in particular the bottlenose dolphin, and an increase in the number of dead dolphins washing up on South West beaches.

Sightings of the bottlenose dolphin have decreased since 1990, and this has caused many environmentalists to believe that local populations are declining.

"Unless immediate action is taken we could be seeing the last last dolphins to grace the South West shores of England," the report said.

"Entanglement in fishing gear is the number one cause of death in stranded cetaceans, particularly common dolphins and harbour porpoises," the report said.

"If we want to reduce human impacts on dolphins and protect the region's dolphins then we need to take urgent action."

Sightings of bottlenose dolphins reached 335 in 1992 but by 2004 the number had dropped to only 60.

And according to the report, just 16 sightings have been reported so far this year.

Dr Lissa Goodwin, fisheries and policy officer for Marine Connection, said: ''We could be having a severe impact on a sub-population of common dolphins that we could be close to wiping out.

"There is also a very real danger that we could be seeing the last of the bottlenose dolphins off the South West shores."

Numbers of dolphin strandings in the South West have increased from 58 in 1990 to more than 150 in 2005, the report found.

Last year, 128 dolphins were found washed up across the Devon and Cornwall coast.

The report recommends an increase in research in specific areas, as well as more immediate measures to reduce dolphin deaths, such as better fisheries management and the deployment of "pingers" on bottom-set gill and tangle-nets.

"Unless immediate action is taken we could be seeing the last dolphins to grace the South West shores of England," the report added.

Some of the best places to see dolphins in the South West include Torbay, Plymouth, Falmouth, Mount's Bay, Land's End, Cape Cornwall and the Isles of Scilly, with the best time of year to see the creatures being between June and August, the Marine Connection said.