Music festival organisers are being urged to do more to tackle legal highs.
Baroness Browning, the government's minister for crime prevention, has written an open letter to the organisers of the UK's top events.
She's concerned about the demand for legal highs and wants more to be done to stop them being taken:
"While people selling these products may give the impression they are legal and safe, they are more than likely not legal, and are not safe."
Legal highs are chemical substances, some of which have effects more closely associated with stronger illegal drugs like cannabis, ecstasy and cocaine.
Mephedrone was previously a "legal high" but was banned as a Class B drug last year.
The minister also warned that substances like plant food and bath salts are often sold as legal highs, but could be harmful if taken.
Organsiers say they now have zero tolerance policy on legal highs and will be searching festival-goers this summer for legal and illegal drugs.
At some festivals stalls selling legal highs are now banned.
Psychoactive substances
"Some of these substances are so novel anyone taking them is playing Russian roulette with their health," she added. "And if you are caught selling or buying them you could face arrest and prosecution.
"The festival season is one of our great summer traditions and we want people to enjoy it responsibly and without breaking the law.
Mephedrone Mephedrone, which was a legal high, was made a Class B drug last year
"We know organisers are alert to this worrying trend and I am inviting them once again to review the measures they have in place.
"We want to help ensure festivals are as safe an environment as possible to help protect the public, especially young people, from the potential harms and risks of all drugs."
The government says it will be working with police, trading standards and organisers at a number of festivals over the summer to help identify emerging new psychoactive substances.
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We have a blanket policy, no legal highs allowed on site. We treat legal drugs the same as illegal drugs, they are banned.
Festival organisers of Leeds, Reading, Big Chill, Bestival, Latitude, V and T in the Park.
It's part of what they're calling a new "forensic early warning system".
The government has also introduced proposals for a new 12-month temporary banning order for new psychoactive substances.
They say they want to protect the public while independent experts, the Advisory Council on the Misuse of Drugs (ACMD), assess any harm they pose.
Festival organisers of Leeds, Reading, Big Chill, Bestival, Latitude, V and T in the park all a blanket policy, no legal highs on site.
"We treat legal highs the same as illegal drug, they are banned."
Glastonbury also said: "We take the issue of legal highs very seriously. We have passed on the contact details for the only trader we have on site out of over 900 traders that trades in legal highs to the local police."
