A Green Party bill to legalise medicinal cannabis will have its first reading in Parliament today after being introduced by Chloe Swarbrick.

The Green Party MP picked up the Bill from fellow MP Julie Anne Genter and has been passionately promoting its benefits to those suffering with a terminal illness and chronic pain ever since.

"What we are seeking to do is provide relief for chronic pain for those with multiple sclerosis and other pain and ailments who could benefit," Ms Swarbrick said.

The Bill is one of two laws up for debate, with Labour introducing a lighter version yesterday which doesn't legalise cannabis but allows someone in the last year of their life to use it.

The Greens' Bill goes much further and would allow patients who are dying and those with chronic pain to grow their own cannabis.

Former Prime Minister Helen Clark is a high-profile backer of the Green Party Bill, tweeting that Ms Swarbrick has set out a compelling case for improving access to medicinal cannabis.

However, to pass into law the Bill will need the support of some National Party members.

National leader Bill English told 1 NEWS the official party line is to support the Labour Bill on cannabis, but not the Green Party's.