I'd take a different approach: CSIRO boss

Two months after announcing hundreds of positions would be axed at the CSIRO, its CEO admits he would do things differently if he had his time over.

But Larry Marshall took a swipe at the media, insisting its "extremely negative" coverage had distressed his staff.

"We are a learning organisation," he told a Senate committee in Canberra on Thursday, conceding to Greens senator Peter Whish-Wilson "of course" he'd doing things differently.

Dr Marshall says he didn't anticipate the magnitude or the level of misrepresentation.

But Labor senator Kim Carr couldn't believe the CEO was surprised.

"The way you've gone about this, it does not surprise me in the slightest that you've managed to create this level of hostility," he said.

Management was not yet able to say how many jobs would be lost in areas such as oceans and atmosphere, insisting the figure of 100 was at the upper limit.

Chief financial officer Hazel Bennett thought it closer to 75.

Dr Marshall ruled out reports that factors such as age, union links and work locations would be considerations in deciding which staff go.

But he tried to put the loses in context, saying the CSIRO had about 180 redundancies on average a year, so 175 people over two financial years was slightly below the 20-year average.

Deputy CEO Craig Roy described the process as a "well-worn track for us unfortunately".

The committee was told the board was notified of the changes in writing on February 2 ahead of the February 4 email to staff.

The minister's office received correspondence on February 1, with the Department of Prime Minister and Cabinet told on February 2.

Management was asked to reappear before the committee at a later date to answer more questions.

The CSIRO Staff Association has written to Science Minister Christopher Pyne asking him to intervene and delay changes until after the federal election.

It claims job losses look to be closer to 450 than 350.