Rapists are slipping GHB into their victims' drinks
GHB, or liquid ecstasy, is likely to be made a Class C drug by next summer.
The move comes after a recommendation to the Home Office by the Advisory Council on Misuse of Drugs.
The body has looked at the issue several times in recent years and found little evidence of widespread misuse of GHB, which is sometimes known as GBH.
Party drug
But concerns have grown that sex attackers are using the colourless, odourless liquid to spike women's drinks, rendering them unconcious for several hours and leaving them with hazy recollections of what happened to them.
Campaigners say hundreds of women are raped each year after their drink or food is spiked with GHB and other drugs like Rohypnol.
Currently legal, GHB - short for gamma hydroxybutyric acid - is often taken in small quantities as a "party drug" to intensify the effects of alcohol and as an aphrodisiac.
It can be bought for as little as £5 a time over the internet or in sex shops.
'Rapists are friends'
When it becomes a classified drug, possession could be punishable with jail terms and suppliers could be sent to prison for up to five years.
A Home Office report earlier this year found drug rapists are more likely to be friends or colleagues than strangers.
The study included interviews with 123 victims and found 70 per cent said they had been attacked by someone they knew.
In August, Westminster Council in London took the extraordinary step of warning women in the area not to accept drinks from men in nightclubs following a string of sex attacks.