Research for the Ministry of Justice has found that too few staff and unfair treatment of prisoners do most to push up violence in jails.
MoJ officials commissioned the study after violence rose in prisons in England and Wales over the past 12 years. It draws together the results of earlier research on prison violence from around the world.
The report says violence in UK prisons has grown significantly year on year since 2015, apart from a temporary fall during COVID.
According to the latest published figures, recorded assaults rose from 22,182 a year in 2015/16 to 30,820 in 2026. Self-harm incidents climbed more steeply over the same period, from 34,665 to 70,632.
Staffing and attitudes
The author of the study is James McGuire, an Emeritus Professor of Forensic Clinical Psychology at Liverpool University. He said higher staff numbers, a stable workforce and few vacancies went hand in hand with lower violence.
By contrast, a higher ratio of prisoners to staff raised stress among staff and led to poorer handling of incidents. That in turn increased the risk of violence.
The review linked demeaning attitudes towards prisoners among staff to higher levels of violence. Conflict between officers also went with more violence among prisoners. Whether prisoners saw responses to their complaints as fair played an important part too.
Prof McGuire found no evidence on how the make-up of the workforce, or the experience of officers, affected violence.
Mixed evidence on education
He also examined several large studies covering rehabilitation programmes, educational and vocational courses, and work. A range of evidence showed that time out of cells, through programmes or other purposeful activity, could affect levels of violence.
Evidence on education and vocational training was mixed. Some studies found that such courses significantly reduced violence, while others found the opposite effect.
Prof McGuire said most of the evidence came from the USA rather than Britain. Even so, he said it pointed towards some constructive approaches across the whole system.
The review suggests that no single measure will solve prison violence. Instead, it says several elements need to work together.
