Associate Health Minister Peter Dunne told the Otago Daily Times he was concerned by reports of the "new synthetic cannabis product K2" in the lower South Island, and the Ministry of Health was working with police to test the product.
"We already have 28 substances under temporary class drug notices, and that has taken more than 50 synthetic cannabis products off the market, and as they come up we take steps to test them, and if they are unsafe, we ban them," Mr Dunne said.
A spokesman for the minister said it was too early to say when or if K2 would be banned.
This comes as Dunedin Senior Sergeants Bruce Ross and Steve Aitken yesterday said K2 made people aggressive and irrational.
The behavioural effects of K2 were worse than those of marijuana, they said.
"With K2, we see violent, irrational behaviour, mood swings and aggression. Most people that come in [to the police station] under the influence of cannabis are pretty mellow," Snr Sgt Aitken said.
Snr Sgt Ross also thought K2 had a worse effect on people than Kronic, another synthetic cannabis product available in New Zealand to people over the age of 18.
"K2 is becoming a real problem. We see people who have smoked it acting in bizarre ways," he said.
On Monday, a 16-year-old Dunedin youth was dealt with by police when, after smoking K2, he allegedly hit his mother during an argument and ran away in his underwear, Snr Sgt Ross said.
The teenager was referred to Youth Aid.
"That's just one example of the type of things we see as a result of K2. It's becoming more and more of a problem," he said.
Those smoking K2 were mostly teenagers and people in their 20s.
Snr Sgt Ross said he was "no expert" on synthetic cannabis and his opinions were based on what he saw as a police officer.
National Poisons Centre toxicologist Dr Leo Schep agreed with police and said, since July, there had been an increase in the number of calls to the centre relating to synthetic cannabis products.
Before that, the Government's temporary measure of banning new substances as they came up appeared to be working, but some of the newest analogues the industry was producing, including K2, appeared to have worse effects than previous ones, Dr Schep said.
"We are seeing increasing trends in psychosis, paranoia and seizures," he said.
He hoped that when the next lot of analogues were banned, the problems would ease.
Mr Dunne said the new legislation to combat the problem would be introduced in Parliament before the end of this year.
"That will fix issues like this ... because it will reverse the onus of proof so the manufacturers of these products will have to prove they are safe, through rigorous testing regimes at their own cost, before anything can come on the market.
"We won't be playing catch-up anymore," he said.
An ODT survey of four Dunedin stores which sold legal highs found all sold variations of the K2 product.
