State-of-the-art technology for detecting submarines has been unveiled by the Ministry of Defence in Fife.
HMS Westminster, which has had the sonar installed
HMS Westminster has been fitted with a low frequency sonar system to improve its defences against increasingly stealthy submarines.
Conservationists are concerned about the impact on whales and dolphins which, they say, could be injured by the sonar emissions.
The navy said protection for marine life had been built into the system.
Critics say the new system is more powerful than previous versions and is more likely to damage mammals.
Protect marine life
HMS Westminster's Commander Andrew Bettom said the MoD did not recognise a moratorium on the use of sonar equipment called for by the European Parliament.
He said environmental research was being carried out to ensure that use of the sonar was "evironmentally friendly".
Dr Sam Healy, a scientist working on behalf of the MoD, said: "The Royal Navy has invested significantly on research into sounds in the water and their effect on marine life.
"The mitigation measures which have been put in place are based on the best available science.
Commander Alex Lochrane: "Military depends on the sea"
"We are fairly confident that this will protect marine life."
Commander Alex Lochrane, of the MoD, said that 80% of the UK's military operations in the future would be transported by sea.
"That's been shown not only through the Falklands War but also through the two Gulf Wars," he said.
"We must continue to protect those assets and the taxpayers' investment."
The Royal Navy plans to introduce the new sonar equipment by 2006.