A homeless charity in Lincoln says a ban on legal highs in the city centre has pushed the problem underground.
The UK’s first city-wide ban on people taking legal highs in public came into force last April.
Breaking the order became a criminal offence, with police given powers to issue on-the-spot fines.
The YMCA’s Malcolm Barham said he welcomed the order, but said more needed to be done to “stop the supply” of psychoactive substances.
More on this and other stories at Lincolnshire Live
“I guess for the general public they are seeing less issues with legal highs, but for those of us who work with people who use these things, nothing has really changed.”
Mr Barham said: “They are awful things that mess with people’s heads and make them do things they wouldn’t normally do.”
One homeless women told the BBC legal highs “are still very easy to get hold of” in the city centre.
A new law making it an offence to supply psychoactive substances is expected to come into force on 6 April.
The Psychoactive Substances Act makes it an offence to produce, supply, offer to supply, possess with intent to supply, possess on custodial premises.
It provides police powers to stop and search people, seize and destroy substances.Lincolnshire Police’s Pat Coates said the force recognised legal highs were still “a significant issue in certain pockets of the community”, but said the ban and forced closure of two “head shops” have had a “significant impact”.
“Prior to the ban, we were getting reports of children becoming ill during the school day having taken these substances,” he said.
Police said new powers would make enforcement easier, and help the force to target dealers.