The Australian Government Information Management Office confirmed yesterday the cost was ''in excess of $500 million''.

The revelation spurred calls for the Federal Government to abandon information technology giants Microsoft and Apple and instead invest in developing free technology.

Advocates of open-source software urged the bureaucracy to follow the examples of France and Brazil, which have largely stopped using private software companies' products in schools, the military and government offices.

Greens communication spokesman Scott Ludlam said the benefits of publicly owned software were more than economic.

''We know [software] costs are sky high and governments are a huge revenue source for companies like Microsoft,'' he said yesterday.

''But there are also very strong public policy grounds for using open-source software. And one is to make sure that government information is accessible to the largest number of people as possible at no cost to them.''

Open-source software is developed by the community and available for free. A popular example is OpenOffice, which performs the same functions as Microsoft's Office, a suite of programs that retails for about $150 to $330.

For more on this story, see today's Canberra Times.