Shoppers have been able to slash their grocery bills by a quarter by ditching the major supermarkets, a report has found, but those in Tasmania and the Northern Territory will miss out on the chance.
Research from consumer group Choice found that Aldi had the lowest prices of the major supermarkets for a basket of average goods.
An average basket of 14 common household items from Aldi cost $51.51 compared to $68.58 at Woolworths and $69.33 at Coles.
The report said the lack of Aldi stores in Tasmania and the NT contributed to higher average grocery prices in those jurisdictions.
Shoppers in Tasmania paid $68.90 on average for the basket of goods, while those in the NT paid $68.82.
On average, customers in the remaining jurisdictions paid between $62 and $64 for the same items.
Choice chief executive Ashley de Silva said where customers lived determined how much they would pay at the checkout.
"If you live in Tasmania or the Northern Territory, you're paying significantly more each week for your groceries," he said.
"However, this is mainly due to the fact that these areas have more limited options for shopping than the rest of the country, with no Aldi in Tassie or the NT."
The basket of items included bread, flour, milk, beef mince, tinned tomatoes, Weet-Bix, apples, carrots, penne, a block of cheese, frozen peas, butter, sugar and tea.
The report was the first of quarterly, government-funded reports into supermarket prices that were set up to help address cost-of-living concerns at the checkout.
Competition Minister Andrew Leigh said the report showed it paid to shop around.
"We've seen a rise in split-basket shopping during the last couple of years as households have felt cost-of-living pressure ... (which) is going to put more competitive pressure on the majors," he told reporters.
Tasmanian senator Tammy Tyrrell bemoaned the lack of supermarket competition in her state.
"Tasmanians are bearing the cost of being put in the too-hard basket by Aldi and other supermarkets," she said on social media.
The federal government has provided Choice with $1.1 million across three years to carry out the reports.
A federal review has called for a mandatory code of conduct between supermarkets and suppliers, with the final report into the code to be handed down by the end of June.
Aldi hailed the report but Coles questioned the survey's methods and offered its own basket price.
"We welcome Choice's contribution however, it is unclear whether like-for-like products are being compared," a Coles spokesperson said.
"Our analysis last week comparing the same basket in NSW shows customers can purchase these products for $59.35 at Coles."
Woolworths emphasised choice in its response to the survey.
"We know many of our customers pick Woolworths because of our wide range of high-quality products at competitive prices in more than 1000 locations across Australia," the company said in a statement.
Greens senator Nick McKim said the report highlighted the need for more players in the market.
"It beggars belief that there could be just one per cent difference in prices between the duopoly," he said.
"The choice between Coles and Woolworths is no choice at all."
