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Warning: This briefing discusses issues around self-harm and suicide which some readers may find distressing.  


Key points

  • England and Wales have the highest per capita prison population in Western Europe. In October 2023, over 88,000 people were imprisoned, in an estate with a maximum capacity of 88,890. This was the highest number recorded 
  • 94% of people in prison are adult men and the adult male prison estate is almost full. The prison estate is operating at 99% of its usable operational capacity and over 60% of prisons are overcrowded. 
  • Drivers of the current prison population growth include changes in sentencing policy (including increased sentence lengths). Other factors include remand, recall, reoffending and policing.  
  • The number of people given immediate custodial sentences has fallen from 98,044 in 2012, to 67,812 in 2022. This suggests that the prison population increase is not driven by more convictions.  
  • Nearing capacity can have negative implications for the safe operation of prisons, and for the health, wellbeing and rehabilitation of people in prison. 
  • Government action to avoid exceeding capacity includes expanding the prison estate and releasing some prisoners up to 18 days early.  
  • As of December 2023, three relevant bills are progressing through Parliament: the Sentencing Bill 2023, the Criminal Justice Bill 2023, and the Victims and Prisoners Bill 2023. Each contains a range of measures, with some likely to reduce the prison population and others likely to increase it.  
  • Various stakeholders have proposed additional policy options, such as the greater use of non-custodial sentences, and interventions to reduce the remand and recall populations.  
  • Some experts in this field have highlighted the role of public opinion in relation to sentencing policy and the relationship between prisons and the wider justice system. Evidence suggests that the public generally overestimate crime rates and underestimate sentence lengths, and that better-informed members of the public are less likely to view sentences as lenient.  
  • More high-quality research is needed to better understand the drivers of increased sentence length and to evaluate health and rehabilitation programmes in the prison context. 


POST is grateful to Cat Jones for researching this briefing and to the Economic and Social Research Council for funding her parliamentary fellowship. 

POSTbriefs are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including:    

  • Members of the POST Board* 
  • Ministry of Justice* 
  • Independent Monitoring Boards* 
  • NHS Health and Justice 
  • Prison Governors Association* 
  • Prison Reform Trust* 
  • Prisons and Probation Ombudsman* 
  • Serco* 
  • Dr Jane Senior and Dr Sarah Leonard, University of Manchester* 
  • Emeritus Professor Julian Roberts, University of Oxford* 
  • Emeritus Professor Nicky Padfield, University of Cambridge* 
  • Kevin Wong, Manchester Metropolitan University* 
  • Professor Andrew Forrester, Cardiff University* 
  • Professor Dorothy Newbury-Birch, Teesside University* 
  • Professor Nick Hardwick, Royal Holloway, University of London* 
  • Professor Seena Fazel, University of Oxford* 

*Denotes people and organisations who acted as external reviewers of the briefing.  

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