The outspoken head of Australia's human rights watchdog, Gillian Triggs, has described the expansion of discretionary ministerial powers that may be exercised with limited or no judicial scrutiny as "a growing threat to democracy".

The defiant president of the Australian Human Rights Commission has also blamed an increasing array of laws that diminish liberties and expand executive power on the failure of successive parliaments to protect democratic rights.

Speaking after she was savaged by Immigration Minister Peter Dutton, Professor Triggs also suggested the indefinite detention of thousands of asylum seekers, most of whom are refugees, has been "essentially punitive" and beyond the power of the national government.

Taken individually, she says the new laws might be justified on the grounds of necessity and proportionality, but "viewed together they are more than the sum of their parts" and an overreach of executive power.

"The overreach of executive power is clear in the yet to be defined proposal that those accused of being jihadists fighting against Australian interests will be stripped of their citizenship if they are potentially dual nationals," she says in a speech to a Human Rights Law Centre dinner in Melbourne on Friday.

"This proposal strikes at the heart of Australia as a largely migrant nation. Not only may this idea violate Australia's international obligation not to render a person stateless, but also the decision may be at the discretion of a minister, without recourse to judicial processes."

The comprehensive critique of the Parliament's willingness to "consider and pass laws that breach democratic freedoms" came after Mr Dutton accused Professor Triggs of making outrageous and offensive claims that were a "complete disgrace".

But Professor Triggs says Mr Dutton has no grounds to attack her and was relying on an inaccurate headline and a newspaper report of comments taken completely out of context.

In the report, in The Australian, it was asserted that Professor Triggs had linked Indonesia's refusal to negotiate on the death sentence for two Australians who were executed in April to the Abbott government's policy of turning back boats.

"At no time did I refer to the recent executions of the two young Australians," Professor Triggs said after Mr Dutton's outburst. "Rather, I spoke of the future need to work diplomatically to reach agreement on ending the death penalty in the region. This reflected my early public commentary on the need for a moratorium on the death penalty."

Mr Dutton also lashed out at Greens senator Sarah Hanson-Young, accusing her of being "an embarrassment to our country" with a track record of making unsubstantiated claims, after private security guards at the Nauru detention centre were accused of spying on her during a visit to the island.

"Rather than attacking the person who was being watched, he should be working out how on earth it happened and ensuring it doesn't happen again," an outraged Senator Hanson-Young replied.

Among the examples of executive overreach cited in Professor Triggs' speech were powers given to ministers to detain indefinitely various classes of individuals, including refugees and asylum seekers, those with infectious diseases, those subject to mandatory admission to drug and alcohol rehabilitation facilities and the mentally ill.

Arguing that the strength of the rule of law is more truly tested when security is threatened, she says: "Many laws introduced with unseemly haste before Christmas in the name of national security go well beyond what might be deemed to be necessary, creating a chilling effect on freedom of speech and the press and breaching the right to privacy."

Professor Triggs argues that a bill of rights would provide greater scope for the courts to assess the validity of legislation and challenge the indefinite detention of asylum seekers, but she concedes this was "highly improbable in the current political environment" and argues the best protection of rights in the future would come from education.

"It has become vital that we develop a normative culture that supports liberties, and challenges executive overreach, even though these liberties may not have the full force of legislation," she said.

Follow us on Twitter