At least 20 people have died in New Zealand as a result of using synthetic cannabis.

A bill increasing the sentences for synthetic cannabis suppliers could pass with the sole support of National and NZ First - despite Labour being in Government.

National backbencher Simeon Brown's amendment to the Psychoactive Substances Act has been pulled out of the member's ballot biscuit tin and will likely have its first reading debate on Wednesday.

Brown's bill would increase the maximum penalty for the suppliers of synthetic cannabis from two years to a maximum of eight years.

STUFF National's Simeon Brown's amendment to the Psychoactive Substances Act has been pulled out of the member's ballot box.

While Labour and the Greens oppose it NZ First have agreed to support it through first reading.

READ MORE:

* Labour and Ardern take the lead in new poll

* Prison muster growing at 'rapid rate'

* Government rejects calls for inquiry into synthetic cannabis

National's 56 votes and NZ First's nine give them a clear majority in the House.

Brown's bill is one of several law and order bills National MPs have in the ballot which could gain the support of NZ First, giving them a solid majority to pass in the House.

Another National member's bill lodged in the ballot would limit the availability of "concurrent sentencing" - likely leading to much longer sentences.

It's understood National have something of a strategy to drive a wedge between Labour and NZ First with members bills they can pass right under Labour's nose.

DAVID UNWIN/STUFF Chloe Swarbrick: "The war on drugs has failed."

"With around 20 reported deaths associated with the consumption of psychoactive substances last year, I expect that this bill will gain full support across Parliament and I will be talking to each party to ensure that it does," Brown said.

"At the moment it's a two year penalty if you're found supplying those products, I think it should be aligned to eight years along with Class C drugs in the Misuse of Drugs Act."

"Ensuring that it progresses successfully through Parliament will allow us to better protect our communities and young people from these harmful drugs."

NZ First's spokesperson for drug issues Darroch Ball confirmed the party would support it through select committee.

"Traditionally NZ First is strong on law and order and we've always been that way," Ball said.

NZ First were at just three per cent in the 1News/Colmar Brunton poll released on Monday - well below the five per cent figure needed to secure re-entry to Parliament. As such they are likely interested in differentiating themselves from the Government when possible.

The party could support the bill through select committee but still reject it at second reading.

NZ First's coalition agreement with Labour has an "agree to disagree" clause along with a commitment to promote the "distinct identity of each party".

Labour have committed to reducing the prison muster by 30 per cent in the next 15 years.

Green MP Chloe Swarbrick said the bill went in the opposite direction of where sensible drug policy all over the world was going.

"The war on drugs has failed. This has been proposed despite all evidence that the war on drugs has failed," Swarbrick said.

She said that people charged with "supply" were not necessarily drug dealers and could be addicts who needed help, not a prison sentence.

"When you are looking at most drug offences, when you have over a certain quantum then it is presumed that you have it for supply," Swarbrick said.

"Why are we wasting Parliament's time on doing this when the direction of travel for pretty much every jurisdiction that's been looking at updating their drug laws has moved towards one that focuses on health and on harm reduction. This is further criminalisation and all evidence shows it is just not going to work."

Since 2015, there had been a more than 20 per cent increase in the prison population, largely due to an increase in the rate of convictions of serious violent and sexual offenders, who boosted the number of long-term prisoners.

The members ballot allows backbench MPs from any party the chance to get a prospective law debated in the House - and even passed, if they can find the numbers for it.

The bills are pulled from biscuit tin and debated on "members night" every second Wednesday.