Police will use the strips when confronted by youths they suspect to be in possession of alcohol but who claim they only have soft drinks.

The strips change colour when dipped into drinks if alcohol is present.

If no colour change shows, the drink can be safely enjoyed as it will not have been contaminated.

'Unacceptable behaviour'

Ch Insp Roger Clayton, who oversees policing in Gloucester, said: "Our young residents know that if they walk down the street with a can or bottle labelled as an alcoholic drink they are likely to have it confiscated, so some will try transferring it to innocent looking packaging.

"This is where these sterile strips come in as they will be able to prove beyond doubt if alcohol is present in a drink."

In 2006 police were called to break up groups of drunken youths who congregated in parks on the day GCSE results came out.

"Such behaviour is unacceptable and will not be tolerated. These strips should prove an effective tool in frontline officers," said Mr Clayton.