Anti-drugs campaigners have expressed dismay after the police backed plans to allow festival goers to test substances such as cocaine and ecstasy for purity before taking them.

The service, which will be offered at a string of live music events this summer, including the Reading and Leeds festivals, is intended to identify potentially dangerous drugs, so that users can make an informed choice.

Festival goers will be able to take illegal drugs to a testing tent, where analysts from an organisation called The Loop, identify the ingredients, before destroying the sample.

The scheme is being rolled out in response to a number of deaths attributed to drugs amongst young people attending music festivals in recent years.

Last year, 17-year-old Lewis Haunch died after taking drugs at Leeds Festival while in the same year two teenagers died at T In The Park in reportedly drug-related incidents.