Consumer NZ has found supermarket specials sometimes aren't so special after tracking online prices at Countdown, New World and Pak'nSave.
For three months, the organisation tracked the prices of 22 items.
At Pak'nSave, the majority of items were on special six or more times. One brand of laundry powder had an "extra low" tag every week, but the price varied from $9 to $12.
At New World, half of the items were on special on six or more occasions. However, one bread brand was $2.99 or higher for 12 weeks.
At Countdown, two to 10 items were on special every week.
"We would argue that if you are being misled about the price or the amount that a product is being discounted, you’re being deceived and that is a breach of the Fair Trading Act," Consumer NZ's chief executive Jon Duffy said.
He told Breakfast that in the wake of its findings it was looking forward to the results of a year-long study into the grocery sector by the Commerce Commission.
The commission's draft report is being released on Thursday.
"It will be very, very interesting to see what the commission finds when it really digs into the level of competition that’s happening to find out whether or not it’s delivering for consumers."
Duffy described the commission's study as "critical" due to a "knowledge vacuum" around supermarkets in New Zealand.
"The supermarkets are closed shops. We don’t know what their margins are, we don’t know what their strategies are," he said.
"Having an independent body come in, put them under a microscope and say ‘actually you are charging monopoly or duopoly prices for your goods and consumers are suffering because of it' ... means we can then have a debate about what the most appropriate outcome is or what the next steps should be..."