A new report from the Helen Clark Foundation has come out in support of legalising cannabis, saying voters should vote "yes" in next year's referendum.
But National's deputy leader Paula Bennett told TVNZ1's Breakfast today she disagrees because of "the unknown" surrounding legislation.
She said she joined the debate 50/50 on the issue, but after doing her own research she now opposes legalising cannabis.
"It's not the kind of anti, morally against cannabis kind of thing," she said. "I've looked into it. The more I've learnt, the more research I've read - I'm now in the 'no' and it's because of the unknown."
Ms Bennett said research is mixed and Canada only legalised cannabis last year, so she wanted New Zealand to wait and learn from them.
But the report from the Helen Clark Foundation claims criminalising cannabis causes social inequity and a drain on police resources. It also gave a list of recommendations to the Government on policies around cannabis legalisation in New Zealand.
Responding to those claims, Ms Bennett criticised former Prime Minister Helen Clark's argument that people shouldn't be criminalised for using the substance when they don't anyway. Only eight people were jailed last year, she said.
Ms Bennett also said legalising the drug wouldn't neccessarily take it off the black market either.
She said even though about 80 per cent of people try the drug, "we've got to be careful about what legalisation means, so does it normalise it?".
"I think we'd all agree we don't want to see teenagers consuming high potency marijuana."
"We don't know if legalisation could lead to more. We're seeing this vaping epidemic with young people - it is hideous. Well actually overseas most people consume marijuana in legalised countries via vaping, so we've got to watch the trends and we just don't have the right kind of information so I'm a bit in the 'let's wait, let's why rush to this next year?'."
Ms Bennett said she would rather see efforts go into combating New Zealand's methamphetamine problem, as well as tackling other "harder" drugs.