The mother of a promising young student who died after taking "liquid cocaine" is calling for the substance to be banned. Hester Stewart, 21, died after mixing gamma-butyrolactone (GBL) with alcohol. GBL is used in inks, dyes and pesticides. But despite being banned for personal use in several countries, including the US, it can be bought in some health food shops in Britain - and over the internet. Now, her mother Maryon is meeting the Home Secretary to demand to know why it has not be classified as a Class C drug. Mrs Stewart, a nutritionist, said: "We called for this meeting because we want to know why GBL isn't classified as a drug at the moment. "My daughter died as a result of consuming it combined with alcohol. It is a colourless liquid which turns into GHB (gamma-hydroxybutyric acid) in the stomach. A small amount of GBL mixed with alcohol can be lethal." She added: "I also want to see a wider awareness and education campaign. GBL is on the market for 50p a dose, which is cheaper than alcohol and may lead some people to try it. We need to give them the information to make wise choices." Miss Stewart was a former pupil at independent Brighton College and was studying molecular medicine at the University of Sussex. Referring to Miss Stewart's sudden death, her mother added: "I'll never come to terms with it. My daughter was planning to become a doctor and help others. I feel she would have wanted me to do this to help save other people's lives." A spokesman said: "The Government is committed to cracking down on legal highs in response to emerging threats to public health. "We are currently consulting on controlling a range of substances, including GBL and BZP, which can harm health. We are determined to tackle drug use in all its forms through tough enforcement, education and, where required, treatment; it is absolutely right that we continue to adapt our drug policy to the changing environment of substance misuse.