Police are carrying out tests on samples of a drug which can cause users to collapse but which is available for purchase in Brighton shops.

Officers from Sussex Police have bought mephedrone at businesses in the city and are now trying to determine exactly what it is made up of.

But they say they can only warn people about the risks involved in taking the drug, which produces similar effects to cocaine and the party drug MDMA.

Despite it being illegal to buy it for human consumption in Britain, it can be bought legally in shops as plant food and is available on the internet.

The drug, nicknamed MCAT or meow, has been compared to a legal form of cocaine. The Home Office says it is investigating the substance as a “priority”.

Police say because there is no legislation involving the possession of the drug for them to enforce they can do little to prevent it being taken.