A Westcountry MEP is calling for an European Commission study into the effect of naval sonars on dolphins, whales and fish.
Some believe the sonar signals may cause bubbles in the animals' tissue
Greenpeace and The Whale and Dolphin Conservation Society estimate that thousands of the creatures die annually on the British coast.
Pair trawling has been blamed for the majority of these deaths.
But recent scientific evidence suggests that sonar activity from war ships could also be playing a part.
Some scientists believe the sonar signals may cause bubbles in the animals' tissue, in much the same way as divers can suffer decompression sickness known as "the bends".
Fishermen in Devon and Cornwall have long been concerned about the impact of sonar on their catches.
Now Caroline Jackson MEP is calling for the European Commission to carry out a study into the impact of naval sonars on the marine environment.
The issue will be debated next week at the Parliament's October Session in Strasbourg.
They say sonar use may need to be regulated to protect the mammals.