A painless way to make kids buzz off?

However, the use of such devices is almost completely unregulated and children's rights campaigners object to them on the grounds that they are indiscriminate - affecting well-behaved and misbehaving young people alike, not to mention infants and babies who may be unable even to object.

Since its release in October 2006, the device - called a Mosquito ultrasonic youth deterrent, by the company that sells it - has proven to be extremely popular south of the border. Almost 3300 security systems were bought within 18 months of their launch. Around 70% of those were installed in the UK, mostly in England and spread around almost every region in the country.

They work because a condition known as "presbycusis" or "age-related hearing loss" means that following their teenage years, most people's ability to hear sounds at frequencies of 18 to 20 kilohertz begins to deteriorate then disappear, according to the system's manufacturer, Compound Security Systems.

The firm says the Mosquito can be activated to make groups of young people who are judged to be a threatening presence on street corners or outside shops, move on of their own accord. It was invented by entrepreneur Howard Stapleton, who claimed to have been inspired when his daughter was bullied by a group of youths outside shops near their home in Merthyr Tydfil.

Now Scotland's commissioner for children and young people, Kathleen Marshall, wants to find out how widely the device's use has spread in Scotland and warns against "zapping" children indiscriminately.

"These devices are discriminatory because they target only young people," she said. "The Mosquito mentality is about zapping young people, moving them on and not addressing what the issues are."

She aso argues that it helps reinforce an unhelfpul and inaccurate perception of young people in some sections of the community: "I think there are much better ways of engaging young people rather than having this attitude of getting them out of the way. Young people don't want to be identified as trouble merely because of the fact of their existence."

Marshall highlights the fact that the effects of these devices are not limited to teenagers but will also be heard by babies, very young children and young people with disabilities. "What about autistic children, who will react particularly badly, or children with visual impairments who rely on their hearing?" she said.

When Marshall learned that Grampian Police were planning to install a Mosquito device in Banff, she wrote to the Chief Constable of the force, Colin McKerracher, expressing her concerns.

McKerracher wrote back, saying that Grampian had decided against deploying the units in the town, describing their use as "disproportionate".

It is difficult to know how many of the devices are already in use here however - as enquiries by The Herald Society have demonstrated.

They are known to have been used or to be in use in other parts of Aberdeenshire, Glasgow, Renfrewshire and Fife and one is even being under consideration in Orkney. And while popular with some police forces, they can be installed by individuals, shopping centres and other businesses. Unlike dispersal orders, Asbos and other deterrents to anti-social behaviour, the police do not have ultimate control over when and where the Mosquito is used.

Local authorities are often unclear about the extent of their use. Phil Walker, managing director of Glasgow Community Safety and Services, confirmed that the devices have been installed in the city, but would not be specific about their locations.

He said: "Mosquito devices have been used in Glasgow, to disrupt and disperse anti-social behaviour in specific and appropriate areas only, for example, where young people congregate and commit acts of anti-social behaviour.

"GCSS themselves have not deployed them but have given advice on deployment to some of our partners."

A spokesperson for Strathclyde Police also confirmed that a device was being used at a chemist shop in Crawfoot in the city.

Two primary schools in Aberdeenshire - Lochpots School in Fraserburgh and Newburgh Mathers School - got the devices in the hope they would stop pupils and other children from climbing on school roofs. A spokesman for Aberdeenshire Council said: "It was agreed that the Mosquito deterrent would provide a safe and cost-effective tool to discourage pupils and youths from climbing on school roofs to ensure their personal safety and to reduce the damage to the buildings that such intrusions caused." However, both devices are believed to have been deactivated.

Renfrewshire Council also tested the device but decided against its use as a permanent fixture. A spokesman said: "It was installed for three weeks at Paisley Town Hall to see if it would have any effect on youths hanging about outside. There were occasions when staff switched on the system, that youths appeared to move away a short time later. Having said that, it was the middle of winter so perhaps they were just moving on anyway.

"We'd keep an open mind about using the system again but have no plans to do so at present."

In her bid to find out how many devices have already been installed, Marshall has been in touch with local councils, police authorities and supermarkets. She has had a mixed response from major supermarket chains. Both Sainsbury's and the Co-op have told her they have no plans to use them, but Somerfield, which already has devices in some English stores, is considering one for Glasgow.

Human Rights campaigners Liberty have also been vocal in their opposition to the use of Mosquitoes. The organisation's director, Shami Chakrabarti, described them as "at worst, a low-level sonic weapon and, at best, a dog-whistle for kids". Chakrabarti added: "Either way, it has no place in a civilised society that values its children and young people and seeks to imbue them with values of dignity and respect. Degrading young people instead of providing opportunities for them is a tragic option whose long-term effect is frightening to imagine."

Paula Evans, policy and parliamentary officer at Children in Scotland, said: "This type of dispersal mechanism affects children of all ages, from infants to young people. It contravenes their right to assemble and to socialise under article 15 of the United Nations Convention on the Rights of the Child. It also fails to address the underlying problem of a shortage, within communities across Scotland, of suitable places for children and young people to meet socially and a shortage of recreational facilities for children and young people to use.

"The same money would be more wisely spent if it were invested in the community to better meet the needs and rights of children and young people instead of simply moving the problem on'."

But a spokesman for Compound Security Systems denied that there are legal or human rights concerns about the use of the devices. "We have thoroughly tested the Mosquito and have gone to extraordinary lengths to ensure that there are no such valid concerns," Si Morris said.

He added: "We have consulted with the National Autism Society and they are quite happy with the product."

Although some autistic people can react badly to sudden loud noises it is a small number and the noise made by a Mosquito is neither loud nor sudden, Morris argued: "There are significantly more autistic people who react badly when confronted with groups of people they do not know."

Morris also said the device was not designed to be left on continuously so should only be used when a property owner perceived a problem with loitering.