The government's plan to ban legal highs could result in young people disproportionately punished and branded criminals, according to The Advisory Council on the Misuse of Drugs (ACMD).

In a letter to Home Secretary Theresa May, the independent drugs body also warned it might discriminate against members of black and minority ethnic groups.

The Psychoactive Substances Bill targets so-called legal highs.

The ACMD supports the "pro-active" bill and says there are positive aspects to it, such as avoiding the delays in the current system.

For example, there is often a time gap between a new drug becoming available and the government's reaction against it.

It also praises the fact the bill does not make possession a criminal offence, only the production and supply.

But it lists eight concerns with the new rules.

One of them is that a person could be prosecuted for "supply and importation" when they have bought a small amount of psychoactive drugs for friends who have bought a substance as a group.

The ACMD refer to this as "social supply" and say that "criminal justice sanctions would be disproportionate to the harm caused by such acts". The top sentence is seven years in prison.

It adds that the bill could seriously inhibit medical and scientific research on psychoactive substances.

Another concern is that illegal dealing networks would be boosted by the closure of "head shops" which sell smoking equipment and other equipment.

The group said the bill as it stands may "not achieve its aims and may produce serious unintended consequences."

Even "helpful evidence-based herbal remedies" could now be criminalised, it added.

The Home Office said that the advsiroy council's advice was "greatly valued".

In a statement it said: "The home secretary has received Professor Les Iversen's letter on the Psychoactive Substances Bill and welcomes the ACMD's support of a move to reduce and prevent harms and preventable deaths caused by these dangerous drugs to young people, adults, families and societies.

"We will respond to the letter and recommendations before the bill is next debated in the House of Lords."

It will next be debated on 14 July.

For guidance on issues around drugs check these BBC Advice pages.

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