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Prison governors in England and Wales have been warned against using cells that do not meet required health and safety standards as pressure on the adult male prison estate continues to increase.
The warning is contained in a six-page document from the Prison Governors' Association (PGA), which was circulated to its members and obtained by the BBC. It reminds governors of their legal responsibilities when allocating cells and says accommodation must be suitable for the number of prisoners being held.
The development comes as prison staff report increasing pressure to place two prisoners in cells originally designed for one person.
According to the leaked Operational Capacity Guidance, prisons must comply with requirements covering matters including cell size, lighting, heating, ventilation and fittings.
The document refers to requirements under the Prisons Act 1952, the Prison Rules and the Young Offender Institution Rules. It states that a cell should only be used when it has been certified as suitable for a prisoner and allows communication with a prison officer.
The guidance also states that the number of prisoners in a prison should not exceed the number of available spaces.
Several prison staff members have told the BBC that overcrowding is making it increasingly difficult for establishments to comply with those requirements.
One governor said some single-occupancy cells were being used for two prisoners because of the pressure on available accommodation. The governor also raised concerns about older prison buildings where heating and plumbing systems may require attention.
Another member of staff said there were concerns about having enough personnel and suitable infrastructure to safely manage additional prisoners.
These accounts are staff reports and do not establish that all prisons are breaching legal requirements.
The adult male prison estate in England and Wales is reported to be operating at about 98.5% capacity.
Prison sources cited by the BBC said there were slightly more than 1,200 spaces remaining across an estate containing approximately 83,400 prisoners.
The available capacity varies considerably between establishments. Some large Victorian-era prisons accommodate more than 1,000 people, while smaller institutions hold populations numbering in the hundreds.
The operational capacity of each prison is not determined solely by its governor. The relevant Prison Group Director considers factors including security, control and the overall number of prisoners when setting the capacity figure.
Some prison staff have expressed concern that management teams are under increasing pressure to accommodate additional prisoners despite limitations in buildings, staffing and available cells.
The Prison Governors' Association guidance has been viewed by some staff as a reminder that operational pressures cannot override legal requirements relating to accommodation.
Former prison governor John Podmore said governors were being required to manage wider pressures within the prison system.
He argued that adding another bed to a cell does not necessarily make the accommodation suitable or safe, while also raising questions about the number of prisoners returning to custody through the recall system.
His comments represent his assessment of the current pressures facing the prison system.
The government is also preparing an early-release programme intended to create additional prison capacity.
Around 4,500 offenders are expected to be released earlier than originally scheduled over a ten-month period.
Under the planned timetable, about 700 prisoners serving sentences of up to 19 months are due to be released on 1 October after serving one-third of their custodial sentence.
A further group of about 650 prisoners serving sentences between 19 months and two years and five months is due to be released on 13 October.
The measures are intended to ease pressure on the prison estate, although some senior prison staff remain concerned about the longer-term effect of continued demand for places.
The Ministry of Justice said the government inherited a prison capacity problem after the number of available places increased by only about 500 over 14 years.
A ministry spokesperson said cells were only doubled up where it was considered safe to do so.
The government says it is working to increase prison capacity by delivering 14,000 additional places, with almost 3,300 already provided. It also plans to convert suitable existing areas into cells, secure land for future prisons and accelerate the removal of foreign national offenders.
The latest warning highlights the continuing challenge of balancing prison capacity, staffing, security and legally required accommodation standards as the number of prisoners remains close to the system's stated limits.
