The power to grant the security agency a controversial "questioning and detention warrant" would rest instead with the Attorney-General – a situation the Law Council of Australia has branded "unprecedented".

The changes being requested by ASIO would also remove a current separate requirement that an independent legal authority, such as a retired judge, is present when a person is being questioned. Rather, oversight of questioning would rest with the intelligence watchdog, the Inspector-General of Intelligence and Security.

Under laws passed in the wake of the September 11 and Bali bombing attacks, ASIO has the power to hold someone for up to seven days and question them if it may "substantially assist the collection of intelligence that is important in relation to a terrorism offence", even if the person isn't a terrorism suspect themselves.

ASIO head Duncan Lewis told a review inquiry last week into the laws that the organisation would "support amendments to the legislation to make the regime more efficient and effective for use in the current security environment".

While ASIO's submission to the inquiry by the Independent National Security Legislation Monitor is confidential, Mr Lewis told the hearing that "it would be most desirable in our view for there to be a streamlining of the warrant authorisation process" whereby authority for the warrants was given by the Attorney-General.

Currently ASIO needs an "issuing authority" in the form of a serving judge to approve the warrant.

The laws include both "questioning warrants", which make it an offence to refuse to answer ASIO's questions and also "questioning and detention warrants", which allow ASIO to have the Australian Federal Police arrest and hold someone so ASIO can question them.

Mr Lewis told the hearing these powers were "fundamental to ASIO's work in responding to the terrorism threat that we face".

Police and intelligence agencies say that terrorism plots in the Islamic State era are increasingly rudimentary and fast-moving, which means processes such as obtaining warrants need to be streamlined as much as possible so authorities can swoop to protect the public.

But the detention warrants have never actually been used in the 11 years they've been in place. Questioning warrants have been used 16 times since 2004, though not since 2009.

The Attorney-General already has the power to approve intelligence-gathering methods such as phone intercepts and surveillance.

But Law Council of Australia director Arthur Moses, SC, who also gave evidence to the inquiry, told Fairfax Media: "We're talking here about persons being detained in custody and deprived of their liberty. That takes it to an entirely different level."

"Western democracies have always taken the position that we do not in effect have a situation where a politician can give that authority … Usually people have the protection of a judicial officer … In my view it's unprecedented.

"We accept and understand that in respect of an evolving security threat environment, sometimes legislation and procedures need to be amended … but we are not aware of any issue that has arisen where ASIO has attempted to obtain a detention warrant and it has not been able to."

Mr Lewis told the inquiry just because they had not been used recently did not mean they weren't vital. They could be used in the future, he said.

He also said it was an "unnecessary belt and braces situation" to require a retired judge or magistrate to sit in the questioning sessions, given the Inspector-General of Intelligence and Security could provide oversight anyway.

University of New South Wales law professor George Williams said countries such as the United States and Britain did not permit such detention for questioning.

"To my knowledge, Australia is the only Western democracy that enables people who are not suspects to be held for up to a week coercively for intelligence-gathering purposes," he said.

"The thought of removing what is one of the few significant checks on the powers is deeply concerning."

But Jacinta Carroll, a counter-terrorism expert at the Australian Strategic Policy Institute and former security official, said the last nine plots disrupted had all posed imminent threats and there was therefore a "logical and compelling case" for streamlining the process.

She said the fact that detention powers had never been used showed ASIO was extremely cautious in the way it used its powers.

She said while this was a "pretty heavy power", it made as much sense for the Attorney-General as first law officer to authorise warrants as a judge.

Bret Walker, SC, the former monitor, said he would want ASIO to show the inquiry examples of where the current law had proved deficient.

"The nature of the powers in some sense are drastic . . . so I would really like to look at real-life, demonstrated deficiency before we look at relaxing safeguards," he said.

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