Mr Godfrey said the relatively small difference between the big two retailers – just $1.80 – "would seem to reflect the intensive process of price monitoring between the duopoly". IGA was the most expensive of the four supermarket chains surveyed as the same basket cost 8 per cent more than at Coles. Including some specials available at the store at the time of shopping cut the bill to $162.56 at Coles and $172.16 at Woolies.

Since then, the big two supermarkets, which hold about 70 per cent of Australia's grocery market, have been engaged in a targeted price war exemplified by the setting of $1 a litre on milk. The stores' marketing has kept pace as Coles' famous catchcry "prices are down" is matched by the Woolies slogan: "Cheap, cheap."

However, a Woolworths spokesman questioned the report. "Comparing a handful of products is rarely an accurate way to judge prices across a whole weekly shop," spokesman Russell Mahoney said. "We survey thousands of prices regularly and we know that when you properly compare like-for-like products, we offer customers a range that competes well with other supermarkets." The Northern Territory was the most expensive place to shop as the average basket cost $170.25, and the ACT was the cheapest at $163.60. NSW and Victoria sit in the middle of the pack at $166.81 and $167.01, a difference of just 20¢ between our most populous states. However, it is difficult to judge the accuracy of these differences, since Choice only surveyed two supermarkets in the Northern Territory (ostensibly a Coles and a Woolworths) and four in the ACT. This compares with 12 in Victoria and 18 in NSW, including Aldi and IGA stores.

Loading The survey follows the release in March of Choice's Consumer Pulse survey. It showed that 75 per cent of respondents named the cost of food and groceries as a financial concern. Only electricity prices caused more concern.