The new pricing code will enable shoppers to compare the value of different brands in real terms, regardless of package size, by using common units of measure such as per kilogram or per gram. All grocery outlets with a floor space of over 1000 square metres must be fully compliant by December 1 and the code will cover advertising as well as online food sales.

The Minister for Competition Policy and Consumer Affairs, Craig Emerson, said the savings figure of $96 was based on overseas surveys, with the published data on savings divided by the total number of households.

Juggling two brands of peanut butter and grappling with the various economic merits of fruit bran cereal versus porridge for breakfast, Dr Emerson launched the official start of unit pricing at the Marrickville Aldi supermarket, a stone's throw from where another launch was meant to have taken place yesterday.

Grocery Choice, developed by the consumer advocacy group Choice under a Federal Government contract, was scrapped last Friday, just six days before its scheduled launch at its Marrickville headquarters. The purpose-designed website was to have partnered the unit pricing scheme under the Government's two-prong strategy to better equip consumers with information on grocery prices.

Dr Emerson sidestepped questions about whether the selection of location to publicise unit pricing might be rubbing salt into the wound of Choice. The relationship between the minister and the not-for-profit organisation is believed to be strained, as is the relationship between Choice and Woolworths and Coles, whose lack of co-operation led to the axing of the website.

"We chose an Aldi supermarket because Aldi supermarkets have been doing [unit pricing] since 2002 and that's great," Dr Emerson said.

Aldi, as its managing director of buying, Matthew Barnes, subsequently pointed out, introduced unit pricing in 2007. A statement released by the National Retailers Association, which represents Woolworths, Coles and Franklins, said thousands of grocery items in supermarkets were already displaying unit prices, but the association nevertheless welcomed a national code.