More prisoners are being transferred to less secure jails to tackle overcrowding crisis, Sky News understands

The prison service is starting to recategorise the security risk of offenders to ease capacity pressures, Sky News understands.

It involves lowering or reconsidering the threshold of certain offenders to move them from the closed prison estate (category A to C) to the open estate (category D) because there are more free cell spaces there.

Examples of this could include discounting adjudications - formal hearings when a prisoner is accused of breaking the rules - for certain offenders, so they don't act as official reasons not to transport them to a lower-security jail.

Prisoners are also categorised according to an Incentives and Earned Privileges (IEP) status. There are different levels - basic, standard and enhanced - based on how they keep to the rules or display a commitment to rehabilitation.

Usually 'enhanced' prisoners take part in meaningful activity - employment and training - making them eligible among other factors, to be transferred to the open estate.

Insiders suggest this system in England and Wales is being rejigged so that greater numbers of 'standard' prisoners can transfer, whereas before it would more typically be those with 'enhanced' status.

Open prisons have minimal security and allow eligible prisoners to spend time on day release away from the prison on license conditions to carry out work or education.

The aim is to help reintegrate them back into society once they leave. As offenders near the end of their sentence, they are housed in open prisons.

Many of those released as part of the early release scheme in October after serving 40% of their sentence were freed from open prisons.

They were the second tranche of offenders freed as part of this scheme, and had been sentenced to five years or more.

Despite early release measures, prisons are still battling a chronic overcrowding crisis. The male estate is almost full, operating at around 97% capacity.

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Sky News understands there continue to be particular pinch points across the country.

Southwest England struggled over the weekend with three space-related 'lockouts' - which means prisoners are held in police suites or transferred to other jails because there is no space.

One inmate is believed to have been transported from Exeter to Cardiff.

A Ministry of Justice spokesperson said: "The new government inherited a prison system on the point of collapse. We took the necessary action to stop our prisons from overflowing and to protect the public.

"This is not a new scheme. Only less-serious offenders who meet a strict criteria are eligible, and the Prison Service can exclude anyone who can't be managed safely in a category D prison."