A quarter of MPs are still struggling to decide whether New Zealand should raise its alcohol purchase age to 20, two days before Parliament is expected to vote on the contentious law change.

A higher purchasing age for bottle stores, dairies and supermarkets was proposed nearly two years ago by the Government but remained a divisive issue.

A Herald survey showed 33 MPs had not decided how they would use their conscience vote on Thursday, when the Alcohol Reform Bill returns to Parliament for its final stages.

Two amendments have been tabled to keep the purchase age at 18 or raise it to 20 for both on-licence and off-licence premises, but none of the three options was a clear winner with MPs.


The survey found 31 MPs wanted the age to remain at 18, 30 said it should be raised to 20, and 27 wanted a split drinking age - 18 for bars and 20 for stores.

Prime Minister John Key confirmed yesterday he would vote for the split age option.

He said a licensed bar environment was well supervised, but off-licences were a source of alcohol for younger people who indulged in binge-drinking.

Mr Key said if the split option was voted down, he would choose to keep the drinking age at 18.

The final result could depend on the order the options are voted on - the business committee will decide this afternoon how to order the vote so that no option is disadvantaged.

If the amendments are voted on first, and the 18 option wins, many of the supporters of the 20 option are expected to transfer their vote to the split age.

National MP for Auckland Central Nikki Kaye tabled the amendment to keep it at 18, arguing that a change put disproportionate blame on young people for alcohol problems all generations were responsible for.

National MP for Hamilton West Tim Macindoe proposed raising the age to 20 to counter "pre-loading" or heavy drinking by young people before going to bars. He was also alarmed by high levels of fetal alcohol syndrome.

MPs could possibly make two conscience votes this week, with a bill on same-sex marriage expected to be debated tomorrow evening.

Most of those fence-sitting on both bills said they were waiting for responses from their constituents before deciding.

How MPs will vote on alcohol purchase age:
* 31 MPs: to keep the alcohol purchase age at 18.
* 30 MPs: to raise the age to 20.
* 27 MPs: to split the drinking age (18 for bars, 20 for off-licences).
* 16 MPs: undecided.
* 12 MPs: undecided but leaning towards a choice.
* 5 MPs: will not say.

Undecided on both alcohol purchase age and gay marriage
* ACT: John Banks
* NATIONAL: Shane Ardern, Maggie Barry, Gerry Brownlee, Chris Finlayson, Steven Joyce, Murray McCully, Lindsay Tisch, Jian Yang.