A new government bill allows the Australian Security Intelligence Organisation to hold someone for questioning for 40 hours to gather information about espionage, foreign interference or politically motivated violence, under a warrant issued by the attorney-general.

David Neal, from the Law Council, told a parliamentary inquiry on Friday that it was a "vast expansion" on the current laws. At the moment ASIO was only allowed to detain people for questioning on terrorism-related offences.

The new law allowed people to be held for questioning even when they were not suspected of being involved - but simply for information gathering, he said. This could include journalists, academics, businesspeople if the issue related to foreign interference, or lawyers.

Politically motivated violence was broadly defined and included threats, "unlawful harm", acts considered likely to lead to violence, or acts that endangered anyone or any group specified by the minister.

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Dr Neal said unlawful harm could include property damage, and "politically motivated" would include protests, allowing people to be questioned in secret for 40 hours for information gathering on protests.

The definition of foreign interference was even more general and included acts in collaboration with foreign powers to affect government processes or "detrimental to the interests of Australia".

Dr Neal said even the new Chinese security legislation applying to Hong Kong limited its application to sedition, not simply "detrimental to the interests" of a country.

The breadth was "extreme", the definition of "detrimental" to Australia's interests "incredibly and perfectly general", and it amounted to "a vast expansion with too little in the way of checks and balances", he said.

"We are very concerned that in legislation of this country that agents of ASIO would be entitled to detain compulsorily people for 40 hours to question them about things which are detrimental to Australia," Dr Neal said.

"... If we are going to have such extraordinary powers, the notion that this is all done behind closed doors and not subject to any level of external scrutiny is frightening."

Labor's Mark Dreyfus, questioning Dr Neal, said, "Under this bill, the attorney-general and the attorney-general alone would be given the power to issue a questioning warrant, which includes the power to authorise the apprehension of a person and the power to compulsorily question a person who has done nothing wrong, and is not even suspected of doing anything wrong, is that correct?"

"Yes it is," Dr Neal said.

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Arrest and search warrants should be issued by a court or at the very least be reviewable by a senior court, Dr Neal said.

"Parliament makes the laws, the executive carries them into effect and the courts determine whether the executive has strayed beyond the powers that it's been given. That's kind of elementary constitutionalism."

But Liberal inquiry MP Tim Wilson accused Dr Neal of grandstanding, using the China comparison to get attention.

"The comparison between the Chinese national security law and this bill is patently absurd," he said, pointing to provisions in the Chinese legislation that define damaging public transport facilities as a form of terrorism and prevent people found guilty from standing for public office.

Mr Wilson told Dr Neal he had failed to take account of the integrity of Australia's court system.

But Law Council policy director Natasha Molt said the Australian law effectively excluded the courts.

"There really is no role here for courts. It is the attorney-general that is authorising these warrants. There are no appropriate checks and balances on that by the courts."

Dr Molt told Mr Wilson that while damage to public property might not fit the definition of terrorism in the Australian law as in the Chinese law, it could come under the definition of politically motivated violence.

Liberal Senator David Fawcett said he failed to see any credible comparison between the new law or ASIO actions and the Chinese national security law, which had been abused with no checks and balances.

"I don't see millions of people lining up to flee Australia and find that a quite disingenuous comparison, given the reality of the checks and balances which are in place," he said.

Dr Neal told him he was missing the point.

"The point is the power of questioning relates currently to terrorism offences. Under the proposal, it will relate to an enormously broader range of things, including as I have said a number of times things which are detrimental to the interests of Australia ...

"Anyone can be questioned about doing things which are detrimental to the interests of Australia as determined by ASIO in the first instance, and that's a massive expansion from being able to question about a terrorist offence."