Hester Stewart had not understood the risk of taking GBL, her family said
A government campaign to tackle "legal highs" has been described as "wholly inadequate" by a victim's family.
Hester Stewart, 21, was found dead at a house in Brighton in April after taking gamma-butyrolactone (GBL) - a substitute for the banned drug GHB.
Her mother Maryon said tougher laws, along with a continuing campaign, were needed to prevent further deaths.
In August, Home Secretary Alan Johnson said GBL would be banned and designated as a class C drug at the end of 2009.
This means users could be punished with a two-year jail term and dealers sentenced for up to 14 years.
The Home Office spokesperson said the new legislation was "only part of the work to tackle so-called legal highs" and an information campaign to educate young people on the dangers of these substances would also begin.
The Crazy Chemist campaign by Frank, aimed at 18-24-year-old clubbers, would highlight the potential danger of party drugs at university freshers' weeks around the country, the spokesman added.
However, Mrs Stewart said: "The Home Office campaign is wholly inadequate."
Mother thinks law failed daughter
Her daughter "would still be with us today" if she had understood the risks, she added.
Miss Stewart's sister Phoebe, 28, said: "It's like the Home Office is paying lip service to the issue, and it is really sad.
"The government is not taking it seriously enough, and for a substance that can kill you within a matter of hours, class C is ludicrous."
Shadow home affairs minister James Brokenshire backed the Stewart family and wrote to Mr Johnson on Friday to urge him to reconsider the classification.
He said: "The fallout from the reclassification of cannabis has left the damaging impression that a class C categorisation does not apply to particularly harmful or dangerous drugs when GBL has very serious risks attached to it."
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