The government is calling for an emergency ban on fishing for sea bass off Devon and Cornwall.
New figures show that 169 dolphins were killed as "bycatch".
It comes after new measures failed to reduce the number of dolphin deaths.
Campaigners have long claimed the sea bass trawlers are responsible for the numbers of dead dolphins found washed up on beaches.
Now Fisheries Minister Ben Bradshaw has asked the European Commission to introduce a ban before the season re-starts in November.
Mr Bradshaw told the Commons he was calling on the EU to close the South West's bass fishery for six months.
Pair trawlers, which use enormous nets, have been been blamed for killing hundreds of dolphins and porpoises.
New figures from a government-funded study show that 169 dolphins were killed as "bycatch" in the bass fishing season from November 2003 to April 2004 - up from 30 in 2002/03.
Mr Bradshaw said the number of dolphin deaths recorded off the region's coast was "unacceptable".
He said: "I have concluded therefore that we need European action to deal with this bycatch before the fishery re-opens in November.
"A detailed case will therefore now be put to the Commission for emergency action under the Common Fisheries Policy to close the offshore fishery to pair trawling. This is necessary as the majority of vessels in the fishery are French.
"I hope that the Commission and other member states accept the seriousness of this situation and we succeed in getting agreement to an emergency closure."
If the British position is not accepted, Mr Bradshaw pledged to close the bass fishery within the national 12-mile limit and seek a limit to fishing boat numbers.
Campaigners welcomed the move, but warned that persuading French fishermen to accept a ban would be difficult.
Lindy Hingley, of Brixham Seawatch, said Thursday's announcement was "a huge step in the right direction".
But added: "The only thing is it is so late. This should have happened years and years ago."
Ms Hingley said local conservationists had found a record 350 dead dolphins and porpoises washed up on Devon and Cornwall's beaches between January and April this year.