"On the day of our survey, Pak'nSave had the lowest prices in the seven centres we visited, including the cheapest prices for milk and budget bread," Consumer NZ chief executive Sue Chetwin said.
The store also claimed top spot in all centres last year, and has held an almost unchallenged position as number one since 2001.
Mystery shoppers visited supermarkets in each centre on the same day and bought from a list of 30 top-selling supermarket products.
Countdown came in second place for price, while New World was third. The supermarket trailed in every centre, including Christchurch and Dunedin where it pipped Countdown on price last year.
A significant number of products purchased at Countdown were on special offer, giving it the edge on New World for selected items, Consumer NZ said.
Between 37 per cent and 50 per cent of items Consumer NZ bought at Countdown were on special - the biggest discount was a 2kg box of Persil laundry powder, reduced by $5.89.
"While special offers can reduce the weekly grocery bill, if an item is routinely discounted, you have to ask how 'special' is the special price?," Ms Chetwin said.
While Consumer New Zealand has put Pak'nSave in the lead for budget buys, competitor Countdown said it was not far behind.
It claimed that its price position had improved on its 2014 survey result and that there was a range of affordable, quality options in its stores around the country.
It said the everyday prices of more than 3000 of its products had dropped since October 2013 as part of its Price Lockdown and Price Drop programme.
The company said a basket of the 100 most commonly purchased items in its supermarkets had come down 0.5 per cent in the year to October.
These products included meat, produce and dairy - items where there could be substantial seasonal and commodity price variations.Countdown's general manager of merchandise, Chris Fisher, said the company had delivered increasingly low prices since its Price Lockdown programme had been implemented.
"Countdown has delivered increasingly low prices, while maintaining our commitment to quality, convenience and range across our network of 182 stores.
"When combined with our extensive range and great store environment, this makes Countdown a great place to shop."
To find out how frequently items are discounted, Consumer NZ also tracked prices for a smaller basket of 10 items over a three-month period. Prices were checked online weekly at Countdown and New World Thorndon, one of two stores at which New World offers online shopping.
At both supermarkets, most of the items in the basket were regularly discounted, Ms Chetwin said.
At New World, a 500g block of Mainland cheese was on special in seven out of the 13 weeks prices were checked. Countdown had the same brand of cheese on special in six out of 13 weeks.
Both stores regularly offered specials on Anchor butter, which was discounted in six out of 13 weeks.
Other items were on special more often. At New World, a 250g block of Whittaker's chocolate was marked as a special in 11 out of 13 weeks. Countdown had the chocolate on special eight times.
Supermarkets aren't the only retailers regularly offering specials, Ms Chetwin said. In October, Consumer NZ reported on products it found routinely on special at Briscoes and Farmers.
"The results of our research lend support to the case for regular price monitoring to ensure consumers aren't being misled about special prices," Ms Chetwin said.
"Stores tempting customers with price promotions must be offering a genuine deal. If they're not, they risk misleading consumers about the savings available and breaching the Fair Trading Act."
CONSUMER PRICE SURVEY
• Mystery shoppers bought from a list of 30 top-selling supermarket products, including food and drink, personal care and cleaning items.
• No fresh meat, fish or produce was included in the list.
• For staples, such as sugar, milk, bread and flour, mystery shoppers were asked to buy a specific pack size, and the cheapest brand.
• But for most items, a specified brand and pack size was given. If it couldn't be found, a similar item was purchased and then bought at all three supermarkets in that city.
• The survey took place in October.
• All items - apart from 10 basic items where shoppers bought the cheapest brand - are the same in each city, but may vary between cities.
