A gadget that gives gangs of unwelcome youths hanging outside shops an earful of ultrasonic soundwaves does not infringe human rights legislation, its inventor has insisted.

Howard Stapleton, MD of Compound Security Systems, has moved to reassure some 250 retailers who have bought the 'Mosquito' contraption following reports that a local authority had banned it from being used.

As first revealed in The Grocer (November 5, 2005, p12), the £495 unit encourages youths to move on by emitting an annoying high-pitched whine that is only audible to under-20s.

Following trials by store owners, police and local authorities, the contraption has become a huge success, notching up total sales of 500 units. And Stapleton revealed this week that he was now in talks with a multibillion-pound company to put it into world-wide manufacture.

However, he has also been working round the clock to prove the unit does not infringe human rights after police chiefs in Newport, Gwent, raised concerns about potential breaches and councillors moved to ban it - even though callouts to a Spar store in the town, where it was being used, slumped by 84%.

Stapleton said he had spent some £10,000 on emergency legal advice. He said Mosquito couldn't be considered a torture device under the Human Rights Act as people were free to move away from it. The legislation also allows for steps to be taken if individuals' actions are deemed to be threatening or intimidating.

He said that the volume of Mosquito's high-pitched tone was only 85 decibels, compared with the typical 120-decibel level of most alarm systems. "If it is used for short periods of time, when required, there is no issue."