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If the law change is passed, nitrous oxide would be controlled as a class C drug under the Misuse of Drugs Act 1971, alongside diazepam, GHB and GBL.

As a drug, GBL is a central nervous system depressant with, as its moniker suggests, similar effects to ecstasy pills.

Producer Liam McMullan, from GBL Productions, said he has had to cancel 30 performances with about 350 people booked in per show.

The Home Office said associated substances GBL and 1,4-BD - which convert to GHB in the body - would also be moved into Class B.

GBL, a colourless liquid that is sold as an industrial cleaner, is only classed as a controlled narcotic when knowingly intended for human consumption.