Police have revealed that 60kg of mephedrone has been seized in West Yorkshire in the year since the drug was made illegal.
They have also arrested about 200 people for offences related to the former "legal high", reclassified as a Class B substance in April 2010.
Mephedrone, also know an M-Cat or Meow Meow, is a stimulant drug with similar effects to ecstasy and cocaine.
Side effects can include insomnia, nose and throat irritations and psychosis.
A mephedrone user can be sent to prison for up to five years, while a dealer can be sentenced to up to 14 years.
Bryan Dent, West Yorkshire Police drugs coordinator, said: "While our agenda is not to criminalise people who use mephedrone it does not mean we will turn a blind eye."
He admitted that while mephedrone use is harmful, the force is focused on users and dealers of harder drugs.
"The largest problem substances for communities are heroin, crack and cocaine and all the issues that go along with that - the gratuitous violence, the threats and intimidation."