Australia's chief scientist has told a Senate estimates hearing she has never been asked to brief Prime Minister Julia Gillard.

Professor Penny Sackett is resigning halfway through her five-year term due to a combination of "personal and professional reasons".

While refusing to comment directly on how she viewed her interactions with the Government, she told the hearing she briefed former prime minister Kevin Rudd only once during his tenure and had never briefed Ms Gillard.

"I have not met, in her role as prime minister, Prime Minister Gillard. I have met with prime minister Rudd to give a direct personal briefing once," she said.

She also confirmed she was not asked to advise Mr Rudd in the lead-up to the Copenhagen climate conference and was not invited to attend.

When quizzed about what improvements could be made to the role of chief scientist, Professor Sackett said it was the Government's responsibility to clarify what role the chief scientist should play.

"I think the responsibility rests firmly with the Government to make it, to decide how the role of chief scientist for Australia will fit into the variety of advice that it receives on matters of science," she said.

'Ignored and shunned'

Opposition science spokeswoman Sophie Mirabella says Professor Sacket is resigning because she was ignored by the Government.

"It's clear the Government has ignored and shunned her. She's supposed to be the Prime Minister's adviser, and guess what? She's never met Ms Gillard," she said.

"No wonder she resigned. She wasn't even invited to be part of Australia's huge delegation of over 100 people to Copenhagen. She wasn't involved in the process of setting targets we negotiated at Copenhagen."

Ms Mirabella says the comments show the Government is squandering the resources of the office.

"If the Prime Minister doesn't even meet with you and you're supposed to be her chief adviser on science, that shows a pretty rude disregard," she said.

"What is surprising is the Government set this office up, it employs 16 people and costs $2.3 million a year. Why wouldn't you use those resources?"

But the Government's Science, Industry and Innovation Minister, Kim Carr, told the hearing Professor Sackett's role was valued by the Government and he met the chief scientist regularly.

"She's performed a very, very important role on behalf of the Australian people, a role that this Government made full-time," he said.

"Professor Sackett has met with me on average once a month. We have regular dialogue on a range of matters, and of course formal briefings are presented."