Recent research from consumer group Choice found the German-owned grocer to be at least $16 cheaper than Coles and Woolworths across 14 common food items, but was dismissed as a "very narrow basket" by the Australian Retailers Association.
But AAP analysis across a wider shop - including cleaning products, personal hygiene items and other family staples along with meat and vegetables - corroborated the Choice findings.
Coles came off worst in the 13-item comparison, which included purchases such as steak and olive oil (Con Chronis/AAP PHOTOS)
AAP's 13-item basket cost $72.90 at Aldi, compared with $80.20 at Woolworths and $89.25 at Coles.
Items such as a 44-pack of nappies ($11.50), a can of tomato soup ($1.10) and Scotch Finger biscuits ($1.25) were priced identically across all three supermarkets.
But Aldi had cheaper steak, olive oil, lettuce and tampons to produce the most cost-effective shop.
Released on Thursday, Choice's data found Aldi's basket to cost $50.79, noticeably cheaper than Coles ($66.22) and Woolworths ($68.37).
Australian Retailers Association chief executive Paul Zahra called Choice's analysis "not a fair or useful comparison" given it could be comparing premium brands with Aldi's private label options.
But AAP's analysis relied on the cheapest available price - including Coles' and Woolworths' own-brand items - across a wider range of products.
The findings come in the same week the consumer watchdog announced it was taking Coles and Woolworths to court over allegations it lied to consumers with misleading specials.
The Australian Competition and Consumer Commission (ACCC) accused the major supermarkets of increasing prices for a brief period before lowering them and moving them to promotions on sale, but at a higher cost than the initial price.
The consumer watchdog is taking Woolworths and Coles to court over allegedly misleading specials. (Joel Carrett/AAP PHOTOS)
The fresh basket analysis coincided with the ACCC releasing the interim report of its separate supermarkets inquiry.
That report found Australia's supermarket scene to be an oligopoly, with Woolworths and Coles accounting for two-thirds of retail sales.
Aldi came in at just nine per cent, despite 20 years of building its market share in Australia.
"Oligopolistic market structures can limit incentives to compete vigorously on price ... we see Woolworths and Coles providing a broadly similar experience to customers through largely undifferentiated product ranges (and) pricing at similar levels," ACCC deputy chair Mick Keogh said.Â
The ACCC also found half of the respondents to its consumer survey compared prices "always" or "most times" before shopping, way up from 17 per cent in 2008.
AAP'S SUPERMARKET COMPARISON
Aldi - $72.90
Woolworths - $80.20
Coles - $89.25
Items analysed - potatoes, lettuce, steak, chicken, olive oil, pasta sauce, instant coffee, soup, biscuits, nappies, shower gel, tampons, laundry liquid.
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