The public are almost evenly split on whether supermarkets should be able to offer wine at rock-bottom prices by selling at below cost, the latest Herald DigiPoll survey shows.

The result has surprised public health expert Doug Sellman, who expected consumers to be more selfish when it came to cheap booze.

The poll comes a week after progress on the Alcohol Reform Bill, which is the platform for government reform on alcohol and a response to a comprehensive Law Commission report on alcohol-related harm.

"Supermarkets have sometimes been criticised for engaging in 'loss leading', a practice that involves selling alcohol at lower prices than that from which it was purchased from the manufacturer," the commission's report said.

Supermarket chains have questioned the link between cheap alcohol and consumption.

The report noted that consumers often viewed cheaper booze as a good thing, amid concerns that it led to people drinking more, and more often.

A slim majority - 50.6 per cent - of DigiPoll respondents said supermarkets should be able to sell wine at below cost; 45.5 per cent disagreed and 3.8 per cent did not know.

The commission said pricing was a "critical factor" in limiting alcohol-related harm, and recommended increasing the excise tax on alcohol by 50 per cent, which would push prices up by about 10 per cent.

It also wanted the Government to investigate minimum pricing, which the Government is doing by asking retailers for pricing data.

Prime Minister John Key has already ruled out an increase in excise tax.

This week Mr Key said a minimum price was a tool against loss-leading and questioned how effective it would be.

"It would make very cheap alcohol maybe slightly less cheap, but it's not going to do the dramatic things that you can do with excise tax on cigarette smoking, where you can price it out of the market," he told NewstalkZB.

Professor Sellman, director of the National Addiction Centre, said supermarkets could still loss-lead if excise tax went up, but a minimum price per standard drink would draw the curtain on "ultra-cheap alcohol".

"People are very price sensitive. A majority of New Zealanders are low drinkers, so an increase in the price is not going to make a big difference to them.

"A minimum price would impact on the 700,000 heavy drinkers.

"It's targeted. It's exactly what we want."