The cost of transitioning from proprietary software to open source could outweigh any benefits of making the switch, according to the Australian Government Information Management Office (AGIMO).

AGIMO's policy and planning division general manager Graham Fry told a Senate Estimates Committee hearing that scoping the potential for a platform change could cost more than it saves.

"Agencies are obliged to consider value for money on each occasion they apply a software," he said.

"That means considering value for money between the alternatives of open source and proprietary software.

"If the cost of assessing it was greater than the cost of the software, you would have to think twice."

The Government spent over $500 million on software annually, according to 2008-09 data from the senate's Finance and Public Administration committee.

A 2007 AGIMO survey revealed that 68 percent of government agencies were either piloting or using open source software.

But further questioning from Greens Senator Scott Ludlam yesterday revealed research had not been undertaken since. AGIMO took on notice a suggestion that the research be revisited.

Centrelink, the Australian Bureau of Statistics and National Archives of Australia were known to use open source products; however, it was up to individual agencies to make procurement decisions, AGIMO said.

Greens spokesperson Senator Scott Ludlam had been pushing for the government to adopt open source software to promote openness and reduce costs.

While open source software may reduce licensing costs, the cost of support could be an issue.

"Open source does not necessarily mean no cost," Fry said. "There cannot be an assumption that we would save by doing that [converting to open source software]."