Sydney's Supermax: Plans to build new prison to house 'most violent' criminals

Some of New South Wales' most violent criminals could be moved closer to Sydney's CBD as the government plans to build a 'mini Supermax' prison.

Goulburn Supermax is a long and risky two-hour-drive from Sydney's courthouses, where terrorists and terror suspects regularly face court.

Long Bay Correctional Centre is being considered as a potential Supermax unit for inmates who are being held on terrorism-related offences.

The NSW Government has confirmed plans for the new High Risk Management Unit which is expected to open mid next year.

More than 40 people across Australia have been charged with terrorism-related offences since 2014.

Majority of those were in NSW.

The prison will be "hardened" for the accused terrorists and is set to be similar to the High Risk Management Unit at Goulburn, regarded as Australia's toughest jail.

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Inmates will be upgraded into single segregation cells with their own small caged 'yards'.

7 News understands monitoring equipment will also be installed and an air-locked enclosure will be built at the front for safely securing inmates.

The new prison will also potentially hold senior Islamic State member Neil Prakash, who was arrested in Turkey, and is now the subject of a federal extradition order.

Terrorism expert Clive Williams said people arrested on terror offences needed to be kept separate from the rest of the prison population.

"They may not need to be held under really tight security conditions," Mr Williams said.

Deputy Opposition Leader Michael Daley said the facility must be "world's best practice" wherever it is built.

"Obviously it would be more convenient to hold him in Sydney, so he has access to his legal team," he said.