Overcrowded jails under a tough on crime government have created a "revolving door" for inmates, a prison officers' union says.

Together union has taken aim at the Queensland government after a damning report found nearly half of the state's prisoners released from custody return to jail within two years.

Queensland Corrective Services did not effectively rehabilitate prisoners and reintegrate them into society, the state's auditor-general report said.

Inmate numbers had surged 54 per cent in a decade to 11,278.

Queensland's Liberal National government was elected in 2024 on a tough on crime campaign but has come under fire over the "rehabilitation failure".

''This report confirms what corrections officers have been warning for years: if prisons are too overcrowded to rehabilitate people, they are less likely to reduce crime,'' Together assistant branch secretary Michael Thomas said.

''You cannot be tough on crime and run a revolving door.

''Rehabilitation failure is a public safety issue, and every prisoner who reoffends because they had no access to programs, education or a job is a failure of the system, not just the individual."

The report found 12 of the state's 13 high-security jails held more prisoners than originally intended as of June 30 2025.

It warned the statewide prison population was expected to remain above built cell capacity for the next 10 years and could exceed "built bed capacity" by 2035.

The report said 44 per cent of prisoners released in 2022-23 returned to custody within two years.

More than 1000 inmates were waiting an average of 16 months to access rehabilitation programs as of March, while almost 5800 prisoners were queued for wellbeing programs, the report said.

Less than half of those leaving custody in 2024-25 received pre-release support such as help setting up bank accounts or connecting with housing and employment services, it found.

However, Corrective Services Minister Laura Gerber on Wednesday rejected suggestions the state's prisons and youth detention centres were operating at unsafe levels.

They were running at about 90 per cent capacity and the government had ''done the work'' to increase beds and programs, she said.

''We have increased capacity by 25 per cent by opening the Wacol Remand Centre,'' Ms Gerber said.

The minister pointed to the commissioning of the new Lockyer Valley Correctional Centre and expansion projects at Townsville and Arthur Gorrie as proof the government had increased capacity.

Premier David Crisafulli also maintained capacity had been increased while his government had toughened penalties and expanded electronic monitoring.

''Without consequences for actions and guardrails, you don't have the ability to keep people on the straight and narrow,'' he said.

The premier said police data showed its law-and-order agenda was working, with a 7.2 per cent fall in victim numbers.