Two major supermarket chains have criticised national data used to compare grocery prices after they were found to be charging customers more than their cheapest rival.
Research from consumer advocacy group Choice crowned Aldi the best for overall value, while IGA was found to be the most expensive.
Both Coles and IGA have pushed back, arguing the data failed to capture the full range of discounts available in their stores.
Undercover shoppers visited 104 supermarkets across Australia in March to compare the prices of 14 common grocery items.
The items included vegetable stock, sour cream, drinking chocolate, butternut pumpkin, quick oats, garlic, and onions.
Choice says the findings are meant to provide a general picture of grocery prices, noting that smaller and independent stores tend to have more fluctuating prices.
Products were matched as closely as possible based on pack size, ingredients and country of origin.
Aldi offered the most value, with the full basket of products costing just $55.35.
Woolworths was not far behind at $58.92, while the Coles basket without specials came in at $59.22.
A Coles spokesperson said the supermarket offered thousands of weekly specials and the reviewed basket does not accurately reflect the full range of products it sells.
The most expensive shop was IGA at $69.74, although it did prove cheapest for carrots and garlic.
IGA said it was "unfair" that prices at small independent stores were being compared with larger supermarkets.
A spokesperson said they had raised concerns with Choice following its earlier report in March.
"It is disappointing that Choice acknowledges the wide variation in product range and store size of the IGA stores surveyed yet still includes their findings regardless," the spokesperson told AAP.
"IGA stores have a differentiated range, specifically tailored to local shoppers with brands you cannot find anywhere else."
Woolworths said it understood the pressures felt by customers and they would continue to reduce prices on hundreds of winter essentials.
Aldi Australia's Jordan Lack said the supermarket would continue to provide quality products and low prices.
While Aldi claimed the top spot in Choice's comparison, separate research by JPMorgan suggests it has been cutting prices to stay competitive.
According to the investment bank, Aldi's June price reductions, which focused on home brand products, marked its largest monthly price cut in 18 months.
The move is believed to be a direct response to Woolworths' recent $100 million investment in its Lower Shelf Price program, launched in May.
In March, the Australian Competition and Consumer Commission released its final report into supermarkets, finding major chains had little incentive to be competitive on pricing due to their large market share.
