NSW will revise its hardline approach to extremists in prison, moving away from mandatory segregation and closer to a Victorian model, as it becomes clear inmates are being further radicalised in the notorious Supermax.

Victoria disperses suspected and convicted extremists throughout its prison system, while NSW keeps suspected and convicted extremists in the same prison unit to reduce the risks of other inmates being radicalised

But NSW Corrective Services commissioner Peter Severin expects Victoria will need to tighten its measures because the criminal networks linked to extremists continue to expand, increasing the risks other inmates could be radicalised behind bars.

The number of sentenced or accused extremists in Australian prisons has almost doubled in the past three years to about 60 people, but there remains little consensus about their treatment.

At least three Australians released from prison after serving terror sentences are suspected to have since died fighting for Islamic State, and terror attackers overseas, including those involved in the Charlie Hebdo killings, were previously jailed extremists.

Other terrorists, including a Brussels suicide bomber, were found to have been radicalised in prison after being jailed in proximity to extremists.

But the lack of clear evidence about what has worked, locally and internationally, means the approach of Australian prisons is largely experimental, authorities agree.

Other states have either no extremist inmates or such small numbers they are treated on a case-by-case basis.

Fairfax Media has also found:

• A national program has been established to train prison guards how to identify radicalised inmates, amid unprecedented rates of conversion to Islam in prison;
• The Brothers Behind Bars charity founded to support Muslim inmates and their families has again had its bank accounts cancelled and Facebook page taken down;
• Victoria plan to treat any woman or child charged with a terror offence the same as any other inmate, despite the model adopted for adult male extremists;
• A new high-security unit at Barwon Prison is seen as ideal for the segregation of extremists, should Victoria move towards the harsher NSW model; and
• Mazen Touma, the most recently released convicted terrorist in Australia, has been described by Mr Severin as completely rehabilitated and a "constructive member of the community".

Mr Severin stopped short of saying the NSW approach, which involves the 35 suspected or convicted terrorists in the state all being housed in the prison known as Supermax, and the banning of communication in Arabic, had failed.

But he said there was anecdotal evidence it intensified the extremist views of some inmates, who may also see being placed in the prison as a badge of honour.

"That's why we want to create these alternative options so they don't become sort of inward looking, that they don't continue radicalising each other which is clearly a situation that is there." he said.

Move prison units capable of holding a variety of inmates based on their level of radicalisation and whether they were awaiting trial would be established, Mr Severin said.

Victorian prison authorities do not plan to change their approach.

Corrections Victoria deputy commissioner Rod Wise said the question of how to deal with suspected or convicted extremists was complex.

"These are challenges that every prison system in the world is facing."

The Community Integrated Support Program, which provides inmates and recently released offenders access to religious scholars in a bid to alter their interpretations of Islam, has been seen as a vital pillar to the Victorian model.

The Islamic Council of Victoria decided to step away from the program shortly before the Brighton siege - which was committed by Yacqub Khayre, an accused terrorist who had been involved in the program - but authorities and community groups are bullish about its future.

Mr Severin said NSW had to establish a similar deradicalisation program, with the only current program in the state's prisons designed for at risk, rather than radicalised, inmates.

Brothers Behind Bars, founded by Wissam Haddad and Junaid Thorne, who have both been accused by authorities of Islamic radicalism, support inmates linked to terrorism and their families across Australia.

Mr Haddad said it was deeply troubling that NSW inmates who were awaiting trial were held in the same unit, but were subject to far harsher conditions, than serial killer Ivan Milat.

Some had not been approved visits with family for more than three months, he said.

During one recent non-contact visit, a Supermax's inmate's mother basically sat in silence with her son because of the ban on Arabic.

"She only knew one word in English, which was a swear word, so she swore and then just sat on the other side of the glass in tears," Mr Haddad said.

He said Westpac had cancelled accounts linked to the charity last week, following a stance taken by ANZ last year.