The Abbott government sought the resignation of the president of the Australian Human Rights Commission Gillian Triggs two weeks before it launched an extraordinary attack on the commission over its report on children in immigration detention.

The request was conveyed orally by an official on behalf of Attorney-General senator George Brandis. It was rejected outright by Professor Triggs, who saw it as an attack on the independence and integrity of the commission and herself.

Fairfax Media understands that no grounds were given for seeking Professor Triggs' resignation and that she was told "some other opportunity" would be available to her if she resigned.

Professor Triggs, a former barrister and academic, was appointed president of the commission in July 2012 for a fixed five-year term that is intended to protect the president from political interference.

She can be sacked for bankruptcy or serious misconduct.

The approach came a fortnight before the government tabled late on Wednesday the commission's The Forgotten Children report calling for a royal commission into the detention of children under Labor and Coalition governments since 1992.

The report found that detention had caused significant mental and physical illness to children and was in breach on Australia's international obligations. It called for the release into the community of more than 300 children in detention on the mainland and on Nauru.

The government was handed the report in November and tabled it late on the last possible day available under convention.

Mr Abbott has branded the report a "transparent stitch-up", saying the commission would have been better advised to write former immigration minister Scott Morrison a congratulatory letter for stopping the boats.

His attacks were echoed by ministers including Senator Brandis, Mr Morrison, and Immigration Minister Peter Dutton.

A spokesman for Senator Brandis declined to offer any comment or answer questions submitted by Fairfax Media, but the Attorney-General and his department secretary, Chris Moraitis, will face questions on the issue when they appear before a Senate committee on February 24.

Professor Triggs, who will appear before the committee on the same day, refused to comment on the push to remove her when contacted by Fairfax Media on Friday.

But she mounted a strong defence of the commission's impartiality, saying it had tabled numerous reports critical of the impact of mandatory immigration detention to the former Labor government and had intervened in the High Court to oppose its so-called "Malaysian solution".

"I am very disappointed that the substance of the report is being ignored for an inaccurate allegation of bias," she said.

The inquiry had been planned to coincide with the 10th anniversary of the commission's first investigation of children in detention and was called "when the government was not releasing children and their period of detention had reached unacceptable levels", she said.

Reports raising concerns about the impact of detention on children had been tabled in 2012 and 2013 during the period of Labor rule, she said.

"To suggest that, all of a sudden, the commission concentrated on the issue because there was a new government is a serious misrepresentation of the facts."

Government criticism of the report has focused on the timing and the fact that it has dramatically reduced the number of children in detention from the peak of almost 2000 under the former government.

But Professor Triggs has said she welcomed the fall in the number of children in detention under the Abbott government from around 1100 to 211 on the mainland and 119 on Nauru. "I totally reject any suggestion that this report is a politicised exercise."

She has also rejected the government's claim that the report is out-of-date, saying more than 300 children are still in detention.

"This is a document of record, but it's a document of a continuing position in relation to these children."

The shadow attorney-general, Mark Dreyfus, said it was shameful that the government had questioned the integrity the Human Rights Commission's leadership.

"Good governments don't attack independent institutions, they respect them," he said. "This allegation is deeply concerning. Senator Brandis must urgently explain his actions."

Labor's immigration spokesman Richard Marles said: "Professor Triggs is an eminent Australian who has been working diligently in a difficult policy area. It is outrageous that this government has sought to besmirch her reputation."

Greens senator Sarah Hanson-Young, described the move as "bullying and intimidation" and an attempt to shut down dissent.

"The government thought it could scare Gillian Triggs out of her job, but it turns out they picked on the wrong person," she said.

Ben Saul, professor of international law at The University of Sydney, defended Professor Triggs and the commission, saying they had performed their roles faithfully.

"The commission's report on children in immigration detention is a credible, impartial, evidence-based assessment of Australia's compliance with its international legal obligations.

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