A Herald on Sunday representative visited 20 Auckland stores this week and at 16 - 80 per cent - made purchases using a card that didn't belong to her.
New Zealand Retailers Association chief executive John Albertson said the results were "very disappointing", particularly during the pre-Christmas rush.
The findings come despite repeated security warnings from banks and credit card companies on the doubling in fraud cases since 2005.
Our representative visited 10 stores in downtown Auckland and 10 at the St Lukes mall. She attempted to make purchases of about $5 using a colleague's National Bank Visa card and made no attempt to copy the signature on the card.
Staff at 16 stores, including some of our top chains, failed to question the conflicting signatures and allowed the purchase.
Most gave the signatures a cursory glance at best, while a few looked suspicious but still let the purchase through.nzherald