Prisoners inside HMP Wandsworth are increasingly at risk of violence and often locked in their cells for 23 hours a day with just 15 minutes of exercise, a worrying report has revealed.

The report by chief inspector of prisons Nick Hardwick, published by the Ministry of Justice today, found that the prison was "unacceptably overcrowded" and faced "severe staffing shortages".

Almost every service at the prison was judged as "unacceptable".

In the past 18 months 13 prisoners have died in the prison - six were self-inflicted and one homicide.

Why are so many men dying inside Wandsworth Prison?

The prison's budget had been slashed by about 25 per cent and 100 staff roles had been lost since the last report in June 2013.

One in five prisoners said they felt unsafe and inspectors observed landings unstaffed for long periods, creating "a potential for violence to take place unnoticed and unchallenged."

Michael Spurr, chief executive of the National Offender Manager Service, said extra staff have since been drafted in from other prisons and the jail is "now providing a limited but decent and consistent regime".

However, the damming report reveals a depressing picture for daily life in the prison, with reduced rehabilitation services designed to prevent prisoners from re-offending.

Mr Hardwick wrote: "Most prisoners were doubled up in small cells designed for one, with an unscreened, shared toilet close to the beds.

"Prisoners struggled to obtain sufficient clothing, bedding and cleaning materials. Call bells went unanswered for long periods.

"The application process which prisoners used to make simple requests was ineffective.

"The third of prisoners who were unemployed - more than 500 men - usually spent 23 hours a day locked in their cells, and the frequent curtailment of activities meant that many more were frequently confined to their cells for most of the day.

"Daily exercise periods might be as little as 15 minutes and staff shortages meant that association periods were restricted and inconsistent so prisoners were unable to use the phones or showers."

The Victorian prison was generally clean and in good repair, but a Listener suite where prisoners met with Samaritans was "dirty and blood-spattered."

The category B jail is the UK's largest prison and held 1,630 men at the time of the report - almost 70 per cent more than its certified accommodation of 963.

Forty per cent of the population - about 700 men - were foreign nationals, about 100 of whom could not speak English.

But the report found most foreign prisoners relied on fellow inmates to translate for them and were "frustrated and anxious" about their inability to get advice about complex extradition issues.

Nearly 500 prisoners were registered to use the prison's drug services and there were about 300 referrals to the prison's mental health team each month.

Mr Hardwick said health services had deteriorated, mainly due to staff shortages, resulting in "poor" nursing care and "weak" medicine management.

Mental health care was "much better", but insufficient to meet demand, with "unacceptably long delays in transferring men to secure mental health facilities."

Mr Spurr said the inspection took place when staff numbers dropped below budgeted levels due to "a sharp unplanned increase in staff turnover".

He added: "As the chief inspector makes clear - there is more to do to achieve the level of purposeful activity and regime required to effectively support prisoners and help reduce reoffending.

"Recruitment of new staff is underway and we are determined to improve outcomes at Wandsworth both for prisoners and for the public over the coming 12 months."

Frances Crook, chief executive of the Howard League for Penal Reform, said: "Over the summer the Ministry of Justice will be modelling budget cuts of between 25 per cent and 40 per cent as its response to the upcoming spending review.

"Such cuts are achievable, but only if demand on prisons like Wandsworth is curtailed.

"The consequences of starving prisons of further resources, while allowing the prison population to climb further, would be more people dying, more failure and ultimately more crime.”

Have you or a friend or relative served time in Wandsworth Prison?

Call Louisa on 020 8722 6335, or email louisa.clarence@london.newsquest.co.uk.