Green MP Chloe Swarbrick says the medical establishment has been slow to pick up medicinal cannabis because of decades of "reefer madness and the war on drugs".
At present, GPs are allowed to prescribe products containing CBD but not THC. To get THC, patients have to see a specialist and get it signed off by the Ministry of Health.
"You actually in certain circumstances when prescribing this product to people do need this THC, which is commonly associated with pscyhoactive properties - but that actually also helps with pain relief," Swarbrick told Newshub Nation on Saturday.
A new proposal from the Government would make it easier for patients to get products containing THC, but there are concerns doctors won't prescribe it.
Medicines containing THC will also be limited to certain forms - edibles and smokable products won't be allowed.
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"Newness proposes novelty, and it proposes challenge and it proposes risk," said Swarbrick. "What that means is GPs are going to have to learn a little bit more about what medicinal cannabis is... Cannabis has been subject to reefer madness and the war on drugs for 40-plus years, and it's going to take some time to unpick that."
Swarbrick says she didn't enter Parliament to loosen New Zealand's drug laws, picking up the portfolio and a Member's Bill that would have legalised grow-your-own medicinal cannabis from Julie Anne Genter, when Genter became a minister in the coalition Government.
But since then she has become a strong advocate for reform, for both health and recreational use.
"They're two different issues completely. The issue of cannabis as a whole is about how we actually deal with the problem that cannabis exists in this country, and it is being used regardless of prohibition. We actually want to look at reducing harm because we know people are presently accessing it.
"Medicinal cannabis is for people who are currently in pain and suffering and are being turned into criminals for accessing the only medicine that works for them."
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Her Bill was voted down, but Swarbrick says she's "largely happy" with what the Government has come up with in its place.
"I think that it strikes the balance between efficacy and safety of products and accessibility and affordability."
National drug spokesperson Paula Bennett has refused to debate Swarbrick on the issue head-to-head since January. Health spokesperson Michael Woodhouse told Newshub Nation the Government's proposed medicinal cannabis scheme could ironically result in increased criminal activity around drugs, rather than wipe them out of the market.
"There's the opportunity to grow cannabis outside, which means security is going to be quite significant... I think there are some dangers in respect to the likelihood that there could be people wanting to go and raid the crop."
Whether New Zealanders will be allowed to use cannabis recreationally is the subject of a referendum that'll be held alongside next year's election.