The prison population in England and Wales reached a total of 87,787 on Friday (Reuters)
Prison population in England and Wales reached total of 87,787 (Reuters)

Overcrowding in prisons increases the risk of inmates reoffending after they are released, a report by a justice watchdog has warned.

The Criminal Justice Alliance said that overcrowding in prisons puts greater strain on prison staff and restricts prisoners' access to educational and training programmes and mental health treatment services.

That, says the organisation, "reduces the likelihood of tackling the cause of offending behaviour".

The prison population has nearly doubled in England and Wales over the last 20 years, from 45,000 to 87,787 - 400 less than the all-time high of 88,179 set last December.

"When prisons are overcrowded, the risk that offenders will commit crimes upon release may even be greater," the report said.

Prisoners serving short-term sentences of less than 12 months are more likely to reoffend once released as they do not often have access to offender management nor are they supervised and supported on release, according to the report.

"Overcrowding has all too often become an accepted part of life in prison," said Vicki Helyar-Cardwell, director of the group which brings together 67 organisations from charities to research groups to trade unions involved in the prison system.

"But while the system is just about coping, it struggles to meet the challenges of an unexpected surge, such as those that followed the riots last year."

After the riots in August, judges were accused of passing down harsh sentences with some defendants receiving sentences four times as long as those found guilty of similar offences in 2010, Ministry of Justice figures showed.

The report looked at ways to deal with overcrowded prisons, such as reducing the number of people imprisoned for non-payment of fines, which averages four people a week.

The report suggests there is a strong case for diverting offenders who have been arrested for cannabis possession from criminal courts.