Prison bosses in NSW have been given repeated warnings that an upcoming ban on smoking, combined with crammed prison cells and poor living conditions, may spark a riot similar to events in Victoria.

Up to 300 inmates who lit fires, smashed windows, torched vehicles, rammed an exit door and armed themselves with makeshift weapons at Ravenhall prison, near Melbourne, were brought under control at 3am on Wednesday.

Authorities believe a ban on smoking that was due to begin on Wednesday sparked the uprising.

In NSW, the government's independent Inspector of Custodial Services warned that a ban on smoking from August 10 will make terrible conditions in the state's prisons even worse.

"Inmates and staff in NSW correctional centres are under significant stress, and prudent policy makers would recognise that even small additional pressures can make the difference between conditions that are uncomfortable and those that are intolerable," John Paget wrote in his April report, Full House: The growth of the inmate population in NSW.

In a damning assessment of the state of NSW prisons, Dr Paget outlined a litany of poor conditions that are exacerbating the risks posed by severe overcrowding.

The prisoner population has hit new records in the past 18 months and half of the state's prisons are operating over capacity.

Inmates are doubling and even tripling up in cells and the average time spent in cells (16 hours) has become the nation's worst, Dr Paget found.

"Confining two or three inmates to cells designed for one or two for prolonged periods, where they shower, eat and defecate, inevitably raises tensions in an already volatile population," he said.

As staff ratios have worsened, the average wait time to see a GP has blown out to one month and work opportunities have declined by 10 per cent, the report found.

"Where the state treats inmates in a way that denies them a modicum of dignity and humanity it should not be surprised if they respond according, with individual acts of non-compliant behaviour escalating into collective disorder, such as riots," Dr Paget wrote.

Brett Collins, co-ordinator of prisoner advocacy group Justice Action, said smoking is the "one pleasure" that many prisoners have and a better solution would be to keep small smoking areas.

"You're only stirring people who are already unstable," he said.

Corrective Services Minister David Elliott said prison staff had a right to a smoke-free workplace.

"The simple message is - if you want to live a normal lifestyle with freedom of choice then don't become an inmate in the NSW prison system," he said.

A Corrective Services NSW spokesman said there has been extensive planning to ensure the smoking ban is introduced smoothly, including therapy for inmates and assistance from Queensland and New Zealand, where bans are in place.

It's understood CSNSW has requested a debrief from their Victorian counterparts on the Ravenhall riot and its causes.

The CSNSW spokesman said that, since Dr Paget conducted his research in October, the Government has allocated $56 million for the creation and management of 1110 new beds and announced the expansion of Parklea Correctional Centre and a new prison in Grafton, providing a further 1000 beds.

Dr Paget expressed concern that health, education and work opportunities had not increased proportionate to the number of beds.