The prison watchdog has warned thousands of life-sentenced prisoners are not being ‘adequately assessed’ before being allowed out of prison.

Inspectors warn official checks are frequently being drawn up long before convicts go on release and do no sufficiently assess the risk convicts pose to the public.

Chief Inspector of Probation Liz Calderbank said: “Assessments in many instances weren’t being thorough enough and weren’t being completed adequately. Often, quite basic elements were missing.”

Chief Inspector of Prisons Nick Hardwick said current checks are inadequate because they tested inmates’ ability to behave well behind bars rather than in the outside world.

He added: “The public would expect assurance that those processes are properly managed, the risk assessments done properly and proper attention is given to that.”

But the Home Office says open prisons, like HMP Sudbury, are the “most effective” way of ensuring inmates are ready to rejoin the community before their release.

And people sent to an open jail need to be ‘rigorously risk assessed’ and categorised as a low-risk to the public before being transferred from higher security facilities.

Here’s how prison categorisation works.

Categorisation is based on the level of risk a prisoner might pose to the public or national security should they escape and the likelihood of their making attempts to do so.

There are four different security categories:

Category A – Category A prisoners are those that would pose the most threat should they escape.

Category B – Category B prisoners do not need to be held in the highest security conditions but the potential for escape should be made very difficult.

Category C – Category C prisoners cannot be trusted in open conditions but unlikely to make a determined escape attempt.

Category D – Category D prisoners deemed to be trusted in open conditions.