Moves by young Act supporters to boost membership by selling cut-price party pills are "grossly irresponsible", Associate Health Minister Jim Anderton says.
The group Act on Campus sold the pills last month for $1 each to Auckland University students who joined their organisation.
Party pills will be illegal from April 1, after legislation classifying them as a class C1 drug was passed this month. Act, the Green and Maori parties voted against the legislation.
But Act on Campus Auckland president Ben Smith said the pills were still legal and there was nothing wrong with the successful promotion, which had signed up 500 people.
"The Government is actually taking away people's personal freedom despite the fact there is no actual real evidence of harm that would stand up to peer review," he told Radio New Zealand.
Act leader Rodney Hide said he was personally against drug taking, but it was not up to him to tell other adults what they should do with their lives.
"Young people are young people and people at universities tend to go to extremes, but you can't smack their bums any more, that's illegal too," he told Radio New Zealand.
But Mr Anderton, who is the minister in charge of the Government's drugs policy, told NZPA the promotion was grossly irresponsible and Act needed to rein in its youth wing.
He said the banning of the pills was not a kneejerk reaction and using them to promote political membership was immoral.
"It's using a harmful drug to induce people at a cut price to join a political party. How much more serious could it get than that?" he said.
"This ingredient has been advised to the Government by an expert committee of clinicians, toxicologists, pathologists and so on as being harmful. What is there about that that anyone does not understand?"
Mr Anderton said he would love to debate the issue with Mr Hide in ACT's lifeline seat of Epsom.
"I bet you there will be a few concerned parents in Epsom who are not appreciating Act selling their kids at Auckland University harmful drugs at a cheap rate."
Act president Garry Mallet said he would talk to the group about the appropriateness of their promotion, even though the group were not under the control of the main party.