Newshub can reveal National is planning a massive broadside aimed at taking down Labour's medicinal cannabis Bill.

The Government thinks it's got them on side, but on Tuesday the Opposition is not only withdrawing its support, it's doubling down and introducing its own more comprehensive Bill legalising medicinal cannabis.

Huhana Hickey lives with multiple sclerosis and uses medicinal cannabis daily to cope with the pain.

The alternatives, such as morphine, simply aren't an option for her - and those drugs are the cheap choice. Medicinal cannabis has cost Ms Hickey nearly $30,000 in the last three years, but she says it's worth it.

"I've got my quality of life back. That's what I'm dreading, every month it's like 'Come on Government, get your act together and start thinking about how we can resolve this issue'."

The Government's medicinal cannabis Bill is at select committee where MPs scrutinise and test the legislation. Health Minister David Clark is optimistic he has everyone on board.

"I'm hopeful that parties will support it, it's good legislation."

But surprise, National is pulling its support, with leader Simon Bridges calling the Labour Bill a wishy-washy vibe.

"I think in good conscience we support medicinal cannabis, we just can't support this un-thought through vibe the Government's put forward."

Newshub understands National's Bill will include a medicinal cannabis identification card issued by doctors, like those used in parts of the US.

National says its Bill is so much more comprehensive and thought out that it will split the Government, with Mr Bridges saying it's "definitely possible" the Greens and New Zealand First could support it.

"Ours is a real law, theirs is just an idea."

Labour's Bill allows for terminally ill people to possess and use cannabis but not grow it. It isn't clear how they're meant to acquire the cannabis without someone breaking the law.

Medicinal cannabis advocates say the Government's taking far too long while people are dying and in chronic pain.

"It's dragging along at a snail's pace, deadlines seem to keep slipping," says Shane Le Brun from Medical Cannabis Awareness NZ.

As of Tuesday there will be another option to consider.

Newshub.