Fiona Parry, whose daughter Eloise died in 2015 after taking the illegal DNP tablets, spoke of her sadness following the death of 21-year-old builder Vaidotas Gerbutavicius.
Miss Parry, from Condover, near Shrewsbury, said there needed to be greater consequences for those involved in the supply and distribution of the tablets, claiming the present legislation did not seem to be working.
Eloise, who lived in Shrewsbury, was also 21 when she died after taking DNP tablets to lose weight.
Bernard Rebelo, 32, from Gosport, Hampshire, was jailed for seven years for her manslaughter.
An inquest in London this week ruled Mr Gerbutavicius died as a result of taking the tablets.
Senior coroner Nadia Persaud branded the drug a "poison" as she called for a Home Office review into the sale of DNP.
"The current legislation is wholly inadequate and in no way an appropriate means by which to deal with offences that can result in the deaths of those who consume DNP," she said.
"Those affected are often young and vulnerable people."
Miss Parry, who has been in touch with Mr Gerbutavicius' family, said those selling the tablets were exploiting a lack of confidence among young people regarding their appearance.
She said the law needed to be changed to provide a meaningful deterrent.
"The consequences need to be greater, so the people involved in the supply and distribution of these substances re-think what they are doing," said added.
"I don't think they are strong enough to do that at the moment."
The inquest was told Barry Wright, from Northern Carolina, US, was jailed for seven years in February after selling the drug to Mr Gerbutavicius.
Since 2017, at least 30 people have died from taking DNP in the UK, the court was told.
The inquest heard how Mr Gerbutavicius telephoned his father, Andrius, shortly before his death, telling him "no one could help" and he would be "dead within the hour".
Eloise, who was studying for a degree in families and childcare at Glyndwr University, Wrexham, died in April 2015 after taking eight of the tablets.
She sent a heart-rending text message to one of her lecturers hours before her death, saying she knew she was going to die.
DNP, or 2,4-Dinitrophenol, was initially used during the First World War as an explosive.
It was briefly marketed as a diet pill in the US in the 1930s, but was found to cause a dangerous increase in temperature and metabolic rate, which could prove fatal. The pills were eventually made illegal.