People caught with “legal highs” like mephedrone face being arrested and having their homes searched.

Senior officers say the chemicals will be treated as illegal until tests show otherwise as they try to protect young people from using dangerous drugs which have not been banned.

The warning comes after health scares over a legal high drug craze in which mephedrone and other substances available over the counter or on the internet have soared in popularity.

The Argus reported claims last month that children as young as 12 or 13 are using mephedrone, some on school buses.

In Brighton and Hove officers are working with the NHS and city council to teach children about mephedrone as part of drugs education in schools and encourage young people with a problem to seek help.

Where people are found with drugs, police say they will be arrested on suspicion of possession controlled drugs until tests show the substances are not illegal.

Legal highs like mephedrone are not prohibited under the Misuse of Drugs Act - but it is illegal to sell them for human consumption. Shops get around this by labelling them for other uses. Mephedrone is sold as a plant food, costing as little as £7 a gram.

The Home Office said mephedrone is being reviewed by the independent Advisory Council on the Misuse of Drugs.

If experts recommend it should be banned, they could be made illegal by the end of next year.