A former electronics apprentice at British Aerospace has developed a gadget which keeps gangs of teenagers away, according to a report in the Daily Telegraph.

The device emits a high-pitched sound which can only be heard by people under the age of 20. Police are said to be backing the Sonic Teenage Deterrent, aka The Mosquito.

The £622 black box sends out an 80 decibel pulsing sound at up to 16Khz which teenagers apparently find unbearable. It can be attached to the front of houses, shops and offices.

The device works because the body's natural ability to detect some frequency wave bands diminishes by adulthood.

Its creator Howard Stapleton said: "The beauty of it is that the noise does not have to be loud, just pitched at the right level which affects teenagers."