The head of Victoria's Adult Parole Board has hit out at Federal Attorney-General George Brandis for spreading "misinformation" about the prison release of Yacqub Khayre, the man at the centre of a terrorist attack in Brighton.

Khayre killed newly married Nick Hao, 36, who was working at an apartment complex in Melbourne's Bayside area on Monday, and took a woman hostage during a siege.

He shot three police officers at the end of the siege before being killed by police.

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Victoria's parole system has come under extensive criticism since the incident, including from Prime Minister Malcolm Turnbull and the federal Attorney-General.

Khayre, 29, had been released on parole after serving a majority of his five-and-a-half-year sentence, convicted on charges relating to a violent robbery.

On Wednesday, Senator Brandis told Sky News that Khayre had been released as soon as his non-parole period was up.

"He'd been given parole after having served the shortest possible custodial period of his sentence, in other words, as soon as the non-parole period has expired, he was immediately given parole," he said.

"He should not have been plainly and in view what has happened."

But parole board chairman Peter Couzens told ABC Radio Melbourne the Attorney-General's claims were "completely wrong".

"I am somewhat frustrated by misinformation from people who ought to know better, like the Commonwealth Attorney-General, he should have got his facts right about the timing of this man's release," he said.

He said Khayre was sentenced with a non-parole period of three years.

"He [made an application for parole], but initially the board declined to consider him for parole, because he had not behaved himself appropriately," he said.

"His final consideration was postponed from March 2015, until the board dealt with it in December of 2016 ... one year and three months after his earliest possible release date."

Senator Brandis later told RN Drive he believed Victoria, and other states, would want to review the information made available to parole boards in light of the incident.

He said it was up to each individual state parole authorities to ensure they have all the information at their disposal to make fully informed decisions.

"The fact he [Khayre] had been implicated in terrorist activities a few years ago was a publicly known fact," he said.

"Plainly, had the parole board been aware of that they may have taken an different view to the issue of parole because obviously a mistake was made with tragic consequences."

'Innocent until proven guilty'

Khayre's links to terrorism have also come under scrutiny since Monday's incident, as he was charged and acquitted by a jury over a plot to attack the Holsworthy Army barracks in Sydney in 2009.

Victorian Premier Daniel Andrews has proposed changes to federal law which would see federal authorities given a direct role in deciding if anyone of interest to them gets parole.

"I stand ready, if necessary, to take the extraordinary step of referring the powers to make parole decisions for those people who are on the terror watch list to the Commonwealth Government so ASIO and the federal police can be directly involved," Mr Andrews said.

Three police officers were shot during the siege in Brighton on Monday. ( ABC News: Patrick Rocca )

On Wednesday, Judge Couzens said the parole board was never informed the Brighton gunman was on a terror watch list before it decided to release him from custody.

But the Attorney-General told Sky News that there "is no watch list as such".

"What there are is a list of the current investigations of people of concern to ASIO," he said.

"At the moment, there are approximately 400 active ASIO investigations underway but beyond that there is a periphery of people who may have come to ASIO's attention in past years."

He said Khayre was not being investigated by ASIO at the time he was granted parole.

Judge Couzens said he stood by the board's decision to grant parole to Khayre based on the information the board had at the time.

"He was acquitted [of terrorism charges] and it seems to me that this golden thread that runs through our criminal justice system has been forgotten, namely one is innocent until proven guilty," he said.

"At the time when the board made its decision, and at the time when this terrible event occurred last Monday, he was not any watch list because no such thing exists.

"He was not the subject of any investigation by ASIO and one can only conclude from that he was not considered to be a risk."

Limiting parole 'extremely unwise'

Judge Couzens also criticised the Prime Minister for his remarks regarding Khayre's eligibility for parole earlier this week.

On Tuesday, Mr Turnbull questioned why Khayre had been granted parole with his long history of violence and past connection to convicted terrorists.

Sorry, this video has expired Melbourne attack: PM asks 'how was this man on parole?'

"It is clear that this is a real issue where people with known records of violence, including people with known terrorist connections, or at least connections with extremists, have been released on parole," Mr Turnbull said.

Judge Couzens said if the Prime Minister was calling for the abolition of parole for anyone who had committed a violent offence it would put the community at more risk.

"This is extremely unwise, because if you don't have parole available for people who have been convicted of any offence, whether it be violent or otherwise, they walk out of prison without any conditions, without any support, without any supervision, without any monitoring, without any ongoing assistance to deal with any underlying conditions that they take out of prison with them," he said.

"The risk is, and I think the expert opinion is consistent with this, is that people who are released on parole are far less likely to become recidivist than those who are released straight."