The Ministry of Health advised against decriminalising medicinal cannabis for those in chronic pain, saying it would lead to major issues over its legal definition.
The advice is contained in a regulatory impact statement, released at the end of last year, on the Government's Misuse of Drugs (Medicinal Cannabis) Amendment Bill.
The bill would mean a terminally ill person could use illicit cannabis without being prosecuted while a comprehensive prescribing scheme is developed. That olive branch, however, was not extended to those in chronic pain, which has prompted many advocates to say the bill does not go far enough.
The impact statement said decriminalising for those in chronic pain would be problematic.
"Chronic pain is difficult to define, subjective, and would potentially cover a large patient group (21 per cent of adults experience chronic pain). Extending this proposal to this group would be likely to result in significant dispute around the definition of chronic pain."
Rebecca Reider, who uses medicinal cannabis, said those in chronic pain should also be able to use cannabis without being criminalised.
"It's great that the Government recognises a compassionate approach to terminally ill patients is needed. But what about non-terminal patients? Why can't the Government show that amnesty to everyone who has a doctor recommend cannabis?"
Drug Foundation executive director Ross Bell also said the provision for those with a terminal illness - defined as someone who can reasonably expect their life to end within 12 months - was too narrow.
"A one-year window simply does not go far enough to cover people with chronic pain and any terminal illness, and needs to be reconsidered by the select committee."
Health Minister David Clark has said that the bill, introduced at the end of last month, was a compassionate measure that would ensure no prosecutions while a new prescribing framework is set up.
The framework would set a minimum quality standard, which the Ministry of Health said was better than a voluntary scheme. The bill does not decriminalise patients who grow their own cannabis, nor those who supply a patient with cannabis.
Bell hoped the new framework around domestic cultivation and manufacture of medical cannabis products would expand the range of products and bring down prices.
Only two medicinal cannabis products are available in New Zealand, and a doctor must apply to the Ministry of Health to prescribe them. Such prescriptions are not government funded.
The bill, which fulfils a 100-day promise, was softened to gain the support of New Zealand First, and will pass with the support of the Greens.
It does not go as far as Green MP Chloe Swarbrick's member's bill, which would allow anyone with a qualifying medical condition to grow, possess or use the cannabis plant or cannabis products for therapeutic purposes, provided they have the support of a registered medical practitioner. A relative or nominated person could also grow cannabis and supply it to the person.
The Government has said those wishing for medicinal cannabis to be more widely available will have a chance to have their say when Swarbrick's bill has its first reading, expected to be a conscience vote.