Retailers have defended the 'mosquito device' used to put off gangs of teenagers from congregating in their premises.
The British Retail Consortium warned that as violent crime on shop staff rose by 50% last year, and the threat of crime doubled, retailers are well within their rights to use the mosquito device, which emits an unpleasant noise that only people under 25 can hear.
A BRC spokesman said: "Not all young people are involved in violence, but given that some retail staff are facing a level of insolence [from teenagers] they have to have the option of doing what they can to protect themselves. They are entitled to discourage threatening groups from hanging around or in their shops."
The BRC pointed out the device is one of many techniques used to deter youths from stations, shops, or public spaces like parks. Some places use blue lighting to deter gangs, others play classical music, he said.
The Association of Convenience Stores (ACS), which represents 33,000 local shops in the UK, has also recommended that shop owners continue to use the device, as a last resort, to deter unwanted gangs in their stores.
Chief executive of ACS, James Lowman, said: "Unfortunately, in many locations around the country retailers are victims of anti-social gangs of youths that congregate around their premises. These youths deter customers, intimidate staff and can commit vandalism and violence. Where a retailer is faced with this problem we fully support the use of a mosquito device sparingly and as a measure of last resort."
Earlier this week the Children's Commissioner for England launched a campaign 'Buzz off', backed by groups including civil liberties group Liberty, calling for a ban on the devices.
Al Aynsley-Green said "The use of measures such as these are simply demonising children and young people, creating a dangerous and widening divide between the young and old."
There are estimated to be 3,500 of the devices in use in England, many at shopping centres.