The Crown's drug-testing laboratory wants more robust regulations around medicinal cannabis.
The Government is permitting an industry around it, but the Institute of Environmental Science and Research says there is still a lot of confusion around cannabis products.
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Spokesperson Mary-Jane McCarthy told Newshub tests showed the quality varies.
"We have seen quite a range of concentration of the cannabinoids, or the active ingredients, some quite high and actually some lower than they were meant to be."
Ms McCarthy said other countries are also concerned about whether the products are safe and the Government needs to be careful about what kind regime it puts in place.
"We definitely want to make sure that the Government looks at other environments overseas and makes the best judgement on what the appropriate scheme for New Zealand is."
The Government passed a Bill allowing the use and sale of medicinal cannabis in December 2018.
The Misuse of Drugs (Medicinal Cannabis) Amendment Bill passed with the support of Labour, New Zealand First and the Green Party.
It passed with 63 votes for the Bill and 53 against.
NZ First and the Greens both won concessions to the Bill, which amends the Misuse of Drugs Act 1975.
A referendum on the personal use of cannabis will be held at the 2020 election, although what the question will be is yet to be announced.