George Brandis's attack on Gillian Triggs, and her testimony that she was asked to resign as president of the Human Rights Commission, shows he has trampled all over the conventions that govern his own role as first law officer, writes Michael Bradley.

A series of bombs were detonated in a Senate estimates hearing this morning.

The president of the Australian Human Rights Commission, Professor Gillian Triggs, confirmed that, earlier this month, she was asked to resign by the secretary of the Attorney-General's Department, who was acting at the request of Attorney General George Brandis.

She says the secretary, Chris Moraitis, told her she would be offered another government job if she fell on her sword. At the same (super awkward) hearing, Brandis then said he had lost confidence in Triggs, that the impartiality of the HRC has been fatally compromised and that he cannot support it if it is not impartial.

This is, wow, extraordinary.

The first law officer of the Commonwealth has gone on record directly accusing the president of the HRC of political bias in the performance of her statutory duties. It would be no less incendiary if he alleged that the Chief Justice of the High Court or the Chief Commissioner of the Federal Police was corrupt.

That's the territory we're in. It's a declaration of war. And it's wrong, very badly wrong.

Under the Australian Human Rights Commission Act, the president of the HRC is appointed by the Governor-General for a fixed term (in Triggs' case, five years) on the advice of the government of the day, and can only be removed by the Governor-General for misbehaviour or incapacity. As with certain other key appointments, this role is designed by statute to be independent and free from political or governmental interference or influence. That makes perfect sense, given that a critical part of the HRC's role is to investigate, report on and make recommendations with respect to human rights issues and the likelihood that this will sometimes conflict with the government's agenda.

The stated grounds for Brandis's unprecedented attack on Triggs is that the HRC's report on children in immigration detention is partisan and politically motivated. It's strange he should have only formed that view in mid-January, as he says, when he had been sitting on the report since October 2014.

The chairman of the Senate committee, Ian McDonald, admitted he has neglected to bother actually reading the report, but let's assume Brandis has read it. Any fair reading discloses that the HRC was equally scathing of the Coalition and the Labor Party when in government, with respect to their treatment of children in detention. If Brandis has a legitimate gripe about the timing of the report, he hasn't articulated it in any proper way, preferring to buy into Tony Abbott's outright attack on Triggs' integrity.

The position of the Attorney-General is unique in the Westminster system. A member of the ruling party and the Cabinet, he or she is nevertheless by convention supposed to have a higher duty as the primary defender of the rule of law and our system of justice. Conventionally, for example, the Attorney-General defends the judiciary from any public attack, whether or not he or she agrees with the courts' decisions.

The legal system is an independent arm of government, separate from the executive and legislative arms, and it is seen to need protection because it is the least able to defend itself. That is the Attorney-General's particular role.

We clothe certain positions with independence and statutory protection from interference, because of their importance to our system of checks and balances. The Human Rights Commissioners are included in this, because they need to have the freedom to say things the government of the day doesn't want to hear. Indeed, in relation to the issue of children in detention, the HRC is saying what almost nobody in Federal Parliament, and much of the community, wants to hear.

Agree or disagree with the outcome, it's incredibly important that the capacity exists to have uncomfortable legal and social issues aired without political interference or governmental suppression.

Brandis's words today are clearly designed to make Triggs' position untenable - to force her to resign. Yet the entrenchment of her tenure by statute was specifically crafted to prevent precisely this outcome. She should not be vulnerable to being forced out, just because the Government doesn't like her or how she performs her role.

If Brandis truly believes she is politically biased, then he should be quietly approaching the Governor-General and asking him to terminate Triggs' appointment on the grounds of misbehaviour. That's called due process.

Instead, Brandis has sought to trash Triggs's reputation in the most public way imaginable. In doing so, he has trampled all over the centuries-old conventions that govern his own role as first law officer.

If Triggs's testimony is correct, the fact that Brandis sought to remove her from her position by offering her another job raises serious questions about his integrity. Where his actions leave us is in the untenable situation that his working relationship with Professor Triggs is irretrievably broken.

Consequently, one of them will have to go. It shouldn't be her.

Michael Bradley is the managing partner of Marque Lawyers, a boutique Sydney law firm.