Health Minister David Clark will introduce a government bill on medicinal cannabis to Parliament tomorrow but it will not be as liberal as Green MP Chloe Swarbrick's bill, which would allow for suffering people to grow, possess or use cannabis for therapeutic purposes.

Clark is keeping a lid on the details of the Government's bill, but indicated that New Zealand First's support for the bill meant that had to be a watered down version of Swarbrick's bill.

"We wanted to make sure that medicinal cannabis is more accessible to people with terminal illnesses or chronic conditions, and the piece of legislation we will introduce will make progress.

"There are some who will wish that we would go further. We believe we've struck a balance which represents good progress, and Parliament will get a chance with Chloe's bill to decide whether it wants to go further."

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He said he would support Swarbrick's bill in a conscience vote when the bill comes up for its first reading.

The Government's bill is expected to answer several issues including allowing access to botanical cannabis products (for vaporising), licensing domestic production, whether CBD (a non-psychoactive cannabinoid) should be available over the counter, and outlining the process for doctors to prescribe cannabis-based products.

Swarbrick's bill, which was originally introduced by Green MP Julie Anne Genter, would allow a person with a qualifying medical condition to cultivate, possess or use the cannabis plant and/or cannabis products for therapeutic purposes, provided they have the support of a registered medical practitioner.

An immediate relative or other nominated person could also do the same so they could administer or supply cannabis to the person.

Opposition leader Bill English had yet to see the bill, and the party was yet to decide whether it would allow a conscience vote.

"If the right process is followed, there's no reason why you'd want to stop people benefiting from a medicinal product that would be good for them."

He said the fact that there were two bills from governing parties showed that they "can't agree".

He said National did not want to see the bill as a "stalking horse" for decriminalisation for personal use, which the Government has committed to holding a referendum on by the next election.

Prime Minister Jacinda Ardern said that the Government's bill would have the support of NZ First and the Greens and would not be a conscience vote. She said it would not include provision for a public referendum.

"There will be a group of people who would have wanted to go further than it does, but this is a bill we know we have support for and it does advance us on the status quo.

"In an MMP Government it's all about making sure you develop a solution which has enough support. That's what we've done."

She said she had not decided whether she would support Swarbrick's bill.

Green Party leader James Shaw said the Greens would not withdraw the private member's bill, called the Misuse of Drugs (Medicinal Cannabis and Other Matters) Amendment Bill.

"That will be in there as an option. But the good news is we know there is also a Government bill that has the numbers to pass the House. If we can also get the numbers for the other bill, then that is great."