Pressure is going on National to allow its MPs a conscience vote on liquor law reforms, sparking concerns about "absolute chaos" in Parliament's debating chamber.

Parliament's business committee, which agrees on the order of debates, is tomorrow set to map out the process for the Alcohol Reform Bill to finally progress.

The bill has been stalled for months as the Government tries to clear space on the Order Paper for it to pass the committee stages.

Changes in the bill include splitting the drinking age by restricting alcohol sales at off-licences to 20-year-olds while leaving it at 18 for licensed premises.

The banning of off-licence sales of ready-to-drink beverages with more than 6 per cent alcohol, restricting display of alcohol to "non-prominent" areas in supermarkets and grocery stores, and plans to clamp down on alcohol advertising are also on the table.

National will only allow its MPs a conscience vote on the age of alcohol purchase part of the bill.

But Labour's 34 MPs will be allowed a conscience vote on the whole bill, including amendments put up by its own MPs.

Labour's shadow leader of the House, Trevor Mallard, said National should also give its MPs a free vote on the whole bill.

"If they don't, then a lot of their individual MPs will be put in an awful position vis-a-vis their electorates," Mr Mallard said.

"I think there is a general view that a lot of this [alcohol law reform] stuff is going in the right direction but not far enough."

He admitted conscience votes on liquor laws had been "messy" in the past because late, inconsistent and poorly drafted amendments had been passed. That had made the law "unnecessarily untidy as a result", he said.

But Labour would put up its substantive amendments much earlier this time, he said.

Green MP Kevin Hague said the bill was pathetic and needed to be made tougher, but there was "nothing magical about alcohol" that made it suitable for a conscience vote.

"They [Labour] are aware that quite a number of National Party MPs actually agree with us and agree with the experts on public health that the bill doesn't go nearly far enough on availability and marketing and some of those other areas," Mr Hague said.

"Their hope is probably to try and change National's behaviour so that National also agrees to conscience votes on those things, in which case, maybe there would be the numbers for stronger measures."

It seemed unlikely that National would be swayed to allow a total conscience vote, however.

"Having a sensible sequence of voting on these [amendments] is going to be important to do, otherwise it could be absolute chaos in the House."

Justice Minister Judith Collins, who is leading the bill, said she was concerned that Labour "can't come up with a coherent position" on the bill, which was "going to cause difficulties during the entire voting process".

"I think they're having difficulty getting a party position on anything and they're wanting to inflict that on everyone else."

- © Fairfax NZ News