The laws, which allow police to hold terror suspects for four days without a court order, were introduced earlier this year to equip law enforcement agencies with more powers to prevent terrorist attacks.

One day after Friday’s Bourke Street terror attack, Chief Commissioner Graham Ashton said he had been briefed by counter-terrorism officers and had told them they would have his support to use the new powers.

“They know they’ve got that available to them. We haven’t deployed that yet on this operation but certainly they’ve got a green light to go down that path and certainly if they think they need to in this case.”

Earlier this year, the Andrews government overhauled counter-terrorism laws, giving police preventative detention powers to hold terror suspects for up to four days without a court order if they feared an attack.

The changes also create a presumption against bail and parole for people deemed to present a terrorism risk.

The laws allow police to detain terror suspects without a court order or warrant for up to four days while children aged 14 and older can be detained for 36 hours.

On Saturday, Premier Daniel Andrews said the preventative detention laws had been controversial but were based on a risk assessment.

“We haven’t simply acknowledged the challenge and the threat. We’ve taken action,” he said.

Victoria’s Terrorism Act was introduced in 2003 as part of a national push to strengthen anti-terrorism measures in the wake of the September 11 attacks and the Bali bombings.

It gave police powers to apply for covert search warrants if an act of terrorism had occurred or was likely to occur, special powers to deal with chemical, biological or radiological attacks, and a new mandatory reporting scheme for the theft or loss of certain chemicals.

Parliament has continually renewed this legislation, and after the London bombings in 2005 it was strengthened to give police proactive and reactive preventative detention orders and new stop, search and seizure powers.

Constitutional lawyer George Williams said federal and state terrorism laws gave police an “extraordinarily broad and extensive range of powers”.

He said Australians were kidding themselves if they thought stronger police powers were the only solution to terrorism.

“The challenge is you have to be able to identify someone,” he said.

“It can be quite a step to say a person is someone of interest to knowing that they are actually a danger. That is a very difficult problem for police and intelligence agencies.”

He said community-based strategies to build resilience and trust with police and intelligence agencies were the missing piece of the puzzle.

“What is needed is a family member mentioning that someone is in trouble or might have a problem,” he said. “If they are fearful and distrustful that doesn't happen.”

University of Melbourne law expert Jeremy Gans said the latest Bourke Street incident

did not indicate any gap in police powers.

“You might have these people who might be operating on their own, or in small groups,” he said. “There is nothing police can do if they don’t know it is happening. The people who draft these powers have exactly this sort of incident, among others, in mind.”