Grocery Commissioner Pierre van Heerden said the commission was still hearing about too many examples of misleading or inaccurate pricing.
He called on the major supermarkets to improve and publicise their refund policies, which he said would create an incentive for them to improve the accuracy of their pricing.
Customers should be able to trust that the price advertised was what they would pay, he said.
"Kiwi consumers expect and deserve better. The continuing level of pricing errors happening across the major supermarkets is simply unacceptable, and I don't believe the major supermarkets are doing enough to fix these problems and get it right for the future."
Van Heerden said the responsibility for fixing the issues sat squarely with the senior management of both Foodstuffs and Woolworths NZ.
The commission had sought a commitment from the chief executives of the three major supermarkets - Woolworths, Pak 'n Save and New World.
"The groceries sector is a $25 billion a year business, so even if errors only make up a very small percentage of sales, the total overcharge paid by Kiwis at the checkout would run to tens of millions of dollars every year and this is unacceptable."
He also said the supermarkets' processes for recording customer complaints were inadequate, and the lack of clarity and reporting meant supermarkets could not identify potential compliance issues.
"Complaint data is a helpful source of information to identify trends and issues so they can be remedied."
While customers played an important role in bringing pricing issues to supermarkets' attention, refund policies across the three major supermarkets were either absent, not advertised clearly, or inadequate in the benefits they offered, van Heerden said.
The commission had stated the following expectations of the major supermarkets:
Review and amend refund policies to demonstrate a commitment to pricing integrity - for example, by offering a full refund on mispriced goods
Prominently promote refund policies
Ensure there are comprehensive policies and processes around pricing complaints, and train staff fully in those matters
The expectations were separate from the ongoing investigations that were underway under the Fair Trading Act, van Heerden said.
While the three major supermarkets had responded positively to the commission's expectations, van Heerden said it would be "watching to see if they follow up their words with action".
