From today, ‘legal highs’ such as GBL, BZP and Spice will become Class C drugs.
GBL (gamma-butaryl lactone), which is said to be popular on the gay club scene, is a liquid used in paint stripper and nail varnish remover.
Its new status as a Class C drug will mean users could face two years in prison and dealers up to 14 years.
It converts to GHB in the human body, which is already a banned substance.
It hit the headlines this year when medical student Hester Stewart, 21, died after taking it in Brighton.
Experienced users tend to measure their doses using pipettes but overdoses can cause death. It is thought that users can become severely addicted to GBL.
In 2008, the Advisory Council on the Misuse of Drugs said it was seeing evidence that GBL was being used by gay men in clubs.
Home secretary Alan Johnson said today: “We are cracking down on so-called ‘legal highs’ which are an emerging threat, particularly to young people.
“That is why we are making a range of these substances illegal from today with ground-breaking legislation which will also ban their related compounds.”
Stewart’s mother Maryon, who campaigned for BGL to be made illegal, said the move did not go far enough.
She said: “In America it’s the equivalent of Class A. Class C doesn’t mean anything, it doesn’t send the right warnings.”
Drug charity Drugscope warned that people could quickly work to mix new, legal compounds to replace banned ones.
This summer, the first specialist clinic to help GBL addicts was set up in London.
Dr James Bell, a consultant in addictions at the Maudsley Hospital in Denmark Hill, said users could become addicted in weeks.