Many West Aucklanders like to think of themselves as independent in thought and action. That trait has made the area a haven for alternative lifestylers and cultivated a tradition of colourful local-body politics. It perhaps also explains why West Auckland is the last area in the North Island where publicly elected district licensing trusts have a monopoly on selling liquor.

The vast majority of New Zealanders long ago saw through the warm fuzzies that underpin the trust concept, and enjoy the convenience and savings of supermarket liquor sales and a choice of private bars. Competition has served them well, as it will West Aucklanders if they overturn the Waitakere and Portage licensing trusts' monopoly in this month's postal ballot.

The poll, which was forced by supermarket chains Progressive Enterprises and Foodstuffs, has prompted a ferocious war of words. That is hardly surprising, given the trusts' ready-made ploy of portraying themselves as defenders of the community against the greed of dastardly big business. In the trusts' idealised world, the past 30 years have seen the proceeds of liquor sales and gambling poured efficiently back into grateful community causes, instead of lining the pockets of wicked shareholders. If only it were so.

In reality, trusts became unpopular with most New Zealanders because they succumbed to the normal stultifying consequences of smallness and monopoly. Their return on investment was poor, their accountability weak and their service to consumers dismal, the trusts serving up booze barns, slack service and inferior financial management. Almost everywhere, grants to community causes were more mirage-like than munificent.

The outcome was unsurprising. Protected monopolies, whether in private or public ownership, will design their businesses for their own convenience, not that of their customers. Being established to make grants to the community, not profits for shareholders, is not a panacea. Indeed, with no need to earn a competitive return for shareholders, there is an obvious temptation for an organisation to pay greater benefits to others with a stake in it, be they suppliers, managers or staff. The earnings lost this way must be recovered through higher prices or lower community distributions. Additionally, of course, there is always a greater potential for malpractice to thrive under restricted trading.

The West Auckland trusts are making much of the record $5.7 million they handed out to community groups in the past financial year. They have pledged another $80 million for community purposes over the next decade - as long as their monopoly remains. They also point to improved service for customers and financial transparency. But it is difficult not to conclude that they have merely reacted to an easily discerned threat to their existence. Should West Aucklanders vote to retain their monopoly, what is to stop monopolistic tendencies reappearing?

The only answer is for the trusts' bars and bottle stores to be exposed to the acid test of competition. If the supermarkets prevail in the poll, that will obviously happen. But even if the trusts win, they must throw liquor sales open. Supermarkets should be allowed to sell liquor without terms or conditions - on special deals, for example. If the trusts' operations are efficient, they will prosper in a competitive environment, and can continue their community donations. If not, it will be clear they have survived only because they are monopolies. And that West Aucklanders have been poorly served by an abnormal market.