MPs will tomorrow take part in a three-option knock out vote to decide New Zealand's drinking age.
The Government's Alcohol Reform Bill returns to Parliament for a clause by clause debate tomorrow.
The legislation will give communities more control over the concentration, location, and hours of sale for alcohol outlets.
It will also introduce new national maximum trading hours of 7am-11pm for off-licences and 8am-4am for on-licences.
But it has been criticised for failing to introduce a minimum pricing regime or restrict high-alcohol "ready-to-drink" beverages.
The most controversial aspect of the bill is a proposal to change the drinking age which MPs will be given a conscience vote on.
Justice Minister Judith Collins said today said MPs would vote on three options: a split age of 18 in bars and 20 at off-licenses, a rise to 20 or keeping it at 18.
"If there's a clear majority on any of those... that wins.
" If there's no clear majority, the least popular drops out, then it's a vote between the remaining two.
"So it's a bit like a National Party selection contest."
The debate would take "as long as parties want it to", she said.
Only Labour was giving their MPs a conscience vote on the entire bill.
"We want to get this bill passed as soon as possible because in the meantime we've got alcohol outlets being opened up all over our communities. Local councils in particular as asking why they can' have more of a say."
Collins said she would vote for a split age but didn't have a view of which option was likely to pass.
If the split age option dropped off, she said she was likely to vote to keep the drinking age at 18 because at that age people could fight for their country and become police officers.
All eight NZ First MPs will vote for raising the drinking age back to 20, with leader Winston Peters saying it had not been made a party vote but all the MPs agreed.
"We've given the young people of this country a chance to have a lower age," he told reporters. "The whole thing has been an absolute disaster."
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