FRESH calls to ban the use of controversial sonic devices to disperse teenage gangs have been made after it emerged three Scottish railway stations have installed and used the system.

The device which violates EU torture laws and is used to stop teenagers gathering has been installed at stations which are frequently targeted by marauding youths.

Known as a “mosquito”, the anti-loitering device emits a high-frequency sound normally audible to under-25s in a bid to stop them congregating.

It has now been confirmed that four devices have been installed at Aberdeen, Hamilton Central and Helensburgh Central stations in a bid to tackle anti-social behaviour.

However campaigners have said the move is discriminatory towards young people, regardless of whether they are misbehaving.

It is claimed they discriminate against teenagers and young adults and fail to distinguish between law-abiding people and would-be troublemakers.

The Scottish Government has previously rejected calls for a ban, although ministers say they disapprove of the technology.

Bruce Adamson, the new Children and Young People’s Commissioner Scotland, said: “The use of Mosquito devices is not a proportionate response to young people meeting in public spaces.

“Anti-loitering devices are a breach of young people’s human rights and their use is indiscriminate and inhumane. We must not tolerate their use in Scotland.

“It’s important to remember that the information released by the Scottish Government is limited only to Transport Scotland, and we don’t know the extent of Mosquito use across the country by both public and private bodies.

“The Scottish Government must listen to the views of young people and move from being ‘not opposed’ to banning the Mosquito to taking the decisive action necessary to ban it.”

The UK has been prolific in its use of mosquitos, at one point there were more than 3,500 installed in sites across the country - compared to 5,000 across Europe as a whole. It does not cause any permanent damage to a person’s hearing.

However, the United Nations and other international human rights bodies have been raising concern about the issue for a number of years.

In 2010 the Parliamentary Assembly of the Council of Europe called on Scotland and other countries to ban the devices, saying it violates legislation prohibiting torture.

ScotRail said it had used the anti-loitering systems occasionally and that they are only activated when anti-social behaviour was taking place.

A ScotRail Alliance spokesman said: “The safety and security of our staff and customers is our priority. Working with other organisations, including Police Scotland, the British Transport Police, trade unions, and local councils, the various measures put in place in recent months have significantly reduced the problem of anti-social behaviour at the stations.”

A Scottish Government spokesman said: "As recently stated in Parliament, Ministers have written to local authorities and other key partners, including Scotrail, Transport Scotland and Police Scotland, to emphasise our strong opposition to the use of these devices.”