• Government’s 2021 commitment to deliver 20,000 new prison places is not expected to be achieved until 2031 – around five years later than planned 
  • Current expansion plans are insufficient to meet estimated future demand, with a projected shortage of 12,400 places by end of 20271  
  • Expansion costs are expected to be at least £4.2bn (80%) above original estimates in 2021 

The prison capacity crisis is the result of previous governments’ failure to ensure that the number of prison places was aligned with criminal justice policies such as sentencing and police numbers. Coupled with delays in the current expansion plans, this has led to a reactive and expensive approach that will not meet future demand or deliver value for money in the long-term, according to a new National Audit Office (NAO) report.

The independent public spending watchdog has found, as of September 2024, HM Prison & Probation Service (HMPPS) has so far created a third (6,518) of the 20,000 additional places it committed to deliver by mid-2020s.2   

The new date for completing the remaining places is 2031 – five years later than expected – increasing pressure on capacity and costing more. Prison capacity is projected to increase more slowly than demand and MoJ currently projects a shortage of 12,400 places by 2027, if demand increases according to its central forecast. It is relying on the current Sentencing Review to reduce demand for prison places and close the gap. 

There are several reasons for delays to the Ministry of Justice’s and HMPPS’s prison expansion plans, including overestimating its ability to gain planning permission for three out of the six new prisons it had planned to build; unrealistic timelines; insufficient understanding of programme requirements and government bodies not working together to prioritise delivery.  

The MoJ and HMPPS now expect the prison expansion plans to cost between £9.4 billion and £10.1 billion, which will be at least £4.2 billion over previous estimates stated in 2021. Contributing to the overspend are several significant cost increases. These include the cost of Rapid Deployment Cells (RDC), units with a lifespan of 15 years, that will deliver one thousand places at least three years later than planned; as well as inflation in the construction sector, where prices have risen by 40%.  

Over 2020 and 2021, the MoJ increased the scale of its prison expansion plans from 13,400 to 20,000 additional places by the mid-2020s. Despite plans to build six new prisons, refurbish existing prisons and install temporary accommodation, HMPPS has been unable to increase prison places in line with demand. This has resulted in the prison estate operating at close to or at full capacity for over two years.  

In October 2024 there were 85,900 people in prison across England and Wales, a 3% reduction since 6 September 2024, following the early release of at least 3,100 prisoners to manage severe capacity issues. 

Government has had to move quickly to respond to the emerging capacity crisis. HMPPS has set out operational red lines it would not cross in managing pressures to ensure the safety of staff and prisoners, this includes restricting crowding to limits it has assessed as safe.   

Government has largely prioritised short-term ways to increase capacity, such as moving prisoners to open prisons before turning to releasing prisoners early when it had exhausted other options.  

However, the MoJ and HMPPS recognise that these actions in response to the capacity issues could impact the effective rehabilitation of prisoners, which in turn may lead to higher reoffending rates and expose the public to a greater safety risk. They are also expensive: HMPPS’s contingency measure to rent police cells overnight (Operation Safeguard) costs nearly five times the average daily cost for a prison place. 

Over the next few years there will be continued risk to the capacity in prisons, because of the poor condition of parts of the estate. A quarter (23,000) of prison places do not meet fire safety standards and HMPPS’s backlog of maintenance works has doubled to £1.8 billion from £0.9 billion in the last four years. HMPPS estimates it would cost £2.8 billon over the next five years to bring the whole estate into a ‘fair’ condition, more than double its current maintenance expenditure. 

The NAO recommends that the MoJ, the Cabinet Office, HM Treasury, the Home Office and other government bodies should work together to:

  • Achieve alignment between government objectives which impact the prison population and the capacity to support these aims 
  • Learn lessons from the current crisis, including the additional costs involved and impact on prisoner outcomes 
  • Provide greater transparency to the public and Parliament, including publishing capacity projections alongside its population projections  

“The Government must learn lessons from the current prison capacity crisis to ensure the long-term resilience and cost effectiveness of the prison estate.”

Gareth Davies, head of the NAO

Read the full report

Increasing the capacity of the prison estate to meet demand

Notes for editors

  1. MoJ is relying on new demand reduction measures to address a projected shortage of 12,400 prison places by the end of 2027, should its central population projection be realised. HMPPS’s current prison expansion plans are insufficient to meet projected future demand. MoJ intends to publish updated demand projections by mid-December 2024. MoJ is relying on new demand measures such as the Sentencing Review, announced in October 2024, to reduce demand for prison places and close the gap between demand and capacity. It does not have any contingency plans for increasing prison capacity as it views it has limited options left to do this. Public knowledge of the capacity gap and wider debate around how to resolve it has to date been restricted as MoJ does not publish its capacity projections (paragraphs 3.5 to 3.7, 3.13 and Figure 9)
  2. MoJ described its aim to deliver 20,000 new places by the mid-2020s as “the largest prison building programme since the Victorian era”. MoJ set itself ambitious timelines as it wanted to deliver places as quickly as possible to keep up with rapidly rising demand (see paragraph 1.7). Nonetheless, its 2021 commitment to build 20,000 new places by the mid-2020s was unrealistic given the time taken to obtain planning permission and build new prisons. For example, HMP Millsike already had planning permission in June 2020 when its outline business case was approved and is due to open in 2025 – MoJ’s plans involved opening three more new prisons by September 2026 despite having no planning permission at that stage.