The drug GHB will be upgraded to class B following its use in a series of "truly sickening crimes", the Home Office has announced.
Currently class C, GHB is a liquid substance that has sedative and anaesthetic effects and is sometimes used recreationally.
It was used by one of the UK's most prolific rapists, Reynhard Sinaga, and serial killer Stephen Port, to sedate their victims.
The Home Office move to reclassify the drug to the same level as other drugs such as cannabis and speed comes following recommendations last year by the independent Advisory Council on the Misuse of Drugs (ACMD), which previously found evidence of a "concerning increase" in the harm GHB causes.
Announcing the decision, home secretary Priti Patel said: "GHB and related substances have been used to commit some truly sickening crimes, including murder, sexual assault and robbery.
"I will do everything in my power to protect people from harm, which is why I am tightening restrictions around these dangerous substances."
She added: "These changes will make the drugs harder to access and introduce tougher penalties for possession."
Those found in unlawful possession of GHB, short for gamma-hydroxybutyric acid, will face tougher penalties and victims will be better protected from their use by criminals, the Home Office said.
An ACMD report released in November last year said GHB and other related substances, known as GHBRS, should be upgraded to class B.
A review of controls on these drugs was commissioned by the Home Secretary in January 2020 amid growing concern over the criminal use of GHB and other similar substances.
Reynhard Sinaga, the UK's most prolific rapist, was jailed in January last year for drugging and raping more than 40 men, with his trials hearing that he laced his victims' drinks with drugs such as GBH to render them unconscious.
Stephen Port murdered four young men in east London between 2014 and 2015 by plying them with illegal substance.
GHB, which is sometimes referred to as liquid ecstasy and typically bought from street dealers or the internet, acts as a sedative, lowering inhibitions and giving users a sense of euphoria, but it can also make them feel sleepy and put them at risk of overdose and death.
The Home Office said it will also bring forward legislation around two substances that can be converted to GHB on ingestion: gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD).
The department said this will mean that those wishing to possess them for legitimate industrial purposes will require a licence.
The necessary legislation will be brought forward "when parliamentary time allows", the Home Office added.
The maximum penalty a person can face for the possession of a class C drug is up to two years in prison, an unlimited fine, or both.
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