Mosquito devices designed to tackle antisocial behaviour could be switched off after concerns by police.

The device emits an irritating frequency which only young people can hear, encouraging them to disperse.

Devices have been used in Chipping Norton, Abingdon and Didcot and praised for cutting yobbish behaviour. But police now want to set limits on their use.

Moves to switch off the devices have been backed by Oxford West and Abingdon MP Evan Harris and Children's Commissioner Sir Albert Aynsley-Green.

Thames Valley Assistant Chief Constable Nick Gargan said: "We are aware that Mosquito devices have been used to good effect to target antisocial behaviour and minor crime caused by some young people.

"However, we are concerned about the indiscriminate nature of these devices, caused by creating an unpleasant noise audible only to people below adult age.

"We will therefore create guidance to specify the limited types of scenario where these devices could be used."

Oxfordshire's first mosquito device, put up outside the Co-op store in Chipping Norton, was removed at the end of last year.

Mosquitos remain in place at the Co-op in Lostock Place, Didcot, and outside shops in Reynolds Way, Abingdon.

Police believe the Reynolds Way Mosquito has cut crime by 50 per cent.

Sir Albert has claimed the devices are an infringement of the rights of children and young people and called for them to be banned.

He said: "I am very encouraged that Thames Valley Police is taking a stand against the use of the Mosquito device.

"However, I would like to see these devices banned completely. There is no scenario in which the targeting of young people in this manner is acceptable."

Michila Lomas, of Design a Cut, in Reynolds Way, Abingdon, said: "We've had no trouble recently. If the police are to discontinue them then hopefully they won't advertise it, otherwise the kids would all know and come back."