The Commerce Commission is putting the retail industry on notice that it has to manage price promotions carefully.
It has warned supermarket company Progressive Enterprises about what it says were misleading promotions for beer.
The commission says the company offered customers savings of 20 - 25% off all beer at three supermarket chains, but calculated that reduction on a theoretical price that in some cases had not applied for eight months.
It says customers should be able to infer cuts would come off the price of beer just before the promotion began, or off the average price of beer.
The commission thinks the practice is fairly widespread in the retail sector and says it's considering how to address the problem.