The Commerce Commission yesterday published an open letter to retailers, saying it was worried about sales promotions that are offered on a continued basis.
It said pricing concerns were the largest source of complaints last year and warned it would prosecute those not following the regulations.
"We receive a significant number of complaints from consumers who have been misled by, or are concerned about, discount sales advertising and price promotions both in-store and online," the letter stated.
"We also see a variety of these practices in the market ourselves."
Consumer NZ chief executive Sue Chetwin said special offers were so common that more than half of products in its 2016 supermarket price survey were found to be regularly on sale.
"Our investigations have found stores routinely promoting the same items as 'specials', giving consumers a misleading impression about the savings available," Chetwin said. "If a product is regularly discounted, the retailer can't claim a reduced price is all that special."
Commissioner Anna Rawlings told the Herald the Commission was hoping to improve trader compliance through education, which was why the letter had been published.
"Consumers look out for sales and we know that sales can drive competition among retailers and value for consumers," Rawlings said.
"However, when price claims are not accurate and discounts are exaggerated, consumers do not get the 'bargain' they believed they were getting. It is also unfair to other retailers who are offering genuine special prices and pricing their goods accurately."