Three types of "legal highs" will be banned today.
* GBL (Gamma-Butyrolactone) is a chemical solvent which is converted in the stomach into the Class C drug GHB (gamma-hydroxybutyrate) nicknamed "liquid ecstasy".
GHB emerged on the party scene in the 1990s and was banned in 2003.
GBL has already been banned for personal use in several countries including the United States, Canada and Sweden but its industrial use as a paint stripper means it is widely available on the internet and even in some health food shops for reportedly as little as 50p per dose.
The UK's Advisory Council on the Misuse of Drugs highlighted last August that the "harms and misuse" of GBL were commensurate with a Class C drug.
The dangers were also highlighted in a report by the European Monitoring Centre for Drugs and Drug Addiction.
It said GBL was becoming more popular as a recreational drug and, despite security measures to limit its use in clubs and pubs, it was regularly being smuggled into London clubs mixed with water in plastic bottles, condoms and balloons.
It is virtually tasteless when diluted.
It said people who bought the drug ranged from clubbers seeking euphoria to people interested in purported anti-ageing remedies or seeking increased sexual function.
The death of student Hester Stewart, 21, in April this year prompted calls for GBL to be outlawed which were led by her family.
Miss Stewart, a cheerleader with the Brighton and Sussex Waves, died after she consumed GBL with her on-off boyfriend Anthony Morrison after returning to his shared house in Brighton following an American football awards ceremony.
Mr Morrison said it was the first time that Ms Stewart, a University of Sussex student studying molecular medicine, had taken the drug, which had been bought online from a site which warned it was not for human consumption.
She was dead when he woke up at 9am on April 6, he told an inquest into her death.
The inquest was told although the level of GBL consumed by Ms Stewart was low and would have led to full recovery in some people, its combination with alcohol proved fatal.
* Synthetic cannabinoids, like the brand Spice, will become a Class B drug, the same classification as cannabis.
Before today's ban, pouches of the drug were widely available on the internet and in so-called "head shops" for around £20 for three grams.
It was sold under brands such as Spice Silver, Spice Gold, Spice Diamond and Spice Yucatan Fire.
The drug was banned in Germany, Austria and France earlier this year.
Reports from Germany suggested some users suffered heart problems after smoking the drug.
Spice and other so-called synthetic cannabinoids had escaped existing UK drugs laws because they did not contain marijuana and are not chemically related to it.
But by spraying synthetic additives on to herbs, dealers can create similar intoxication in users to that caused by THC, the active ingredient in cannabis.
Analysis of samples of Spice showed it had a "higher potency" than THC.
* BZP (Benzylpiperazine) is used to worm animals and as a fertiliser but has become popular for recreational use as it can have a similar effect to amphetamine.
It can cause a rush of energy, agitation, vomiting and headaches.
The drug comes in many shapes and forms, including pills and powders.
Some websites have marketed it as legal ecstasy and sell it for as little as £1 a tablet but it has already been banned in countries including America, Australia and Japan.Reuse content