The New South Wales Government is considering putting three beds in some maximum security prison cells and mattresses on the floors in others as figures show the state's prison population has reached a record.

Key points: Inmates in NSW jails reach record numbers

Inmates in NSW jails reach record numbers Largest increases for dangerous acts, sexual assaults, fraud and abduction

Largest increases for dangerous acts, sexual assaults, fraud and abduction Opposition says overcrowding leads to violence

NSW Bureau of Crime Statistics (BOCSAR) data shows the adult prison population grew by more than 9 per cent between April 2015 and March 2016 to 12,390.

BOCSAR attributed the rise to growth in the number of prisoners on remand, with the largest increase for prisoners charged with dangerous/negligent acts, sexual assault, fraud and abduction/harrasment.

As the Government struggled with the challenge of prison overcrowding, the NSW Opposition obtained documents showing Corrective Services proposals to cram more than 740 extra prisoners into the system in the short-term.

The document provides a breakdown of proposals to add beds to individual prisons, including 60 extra beds for John Morony Correctional Complex at Windsor and 57 for Grafton prison.

The proposal includes converting single prisoner cells into doubles at Goulburn jail to create an extra 74 beds, and opening an unused wing of the Supermax section to provide for an extra 36 inmates.

The document details plans to put three beds in a cell or place extra mattresses on the floor at a number of other maximum security prisons, although not al the proposals have been approved by the Commissioner.

Extra beds a 'bandaid fix', Opposition says

Opposition corrections spokesman Guy Zangari said the proposals were a recipe for disaster.

"We know that violence is already escalating inside the prison walls due to overcrowding and the sickening attack on an inmate recently highlighted the failure of the system under Minister David Elliot's watch," Mr Zangari said.

"These are all stop-gap measures, they are bandaid-fix solutions."

He said if the Government did proceed with the proposals it would need to hire extra prison guards.

"There are 200 full-time equivalent positions not yet filled within the system," Mr Zangari said.

"If the Government goes down the road of putting three maximum security prisoners into a cell it must make sure that the security is increased and there are more prison officers on the ground to deal with the issue."

A spokeswoman for Correction Minister David Elliot said the record prisoner population was a challenge for the system.

"This working document shows Corrective Services is in constant discussion with the union about ways to increase short-term capacity while maintaining the safety and security of staff and inmates," she said.

"The NSW Government has delivered more than 2,800 additional beds since March 2014 and is progressing plans to build a new prison in Grafton and expand Parklea."