By Melanie Griffiths and

Peter William Walsh

This briefing examines immigration detention in the UK. It discusses who is detained, for how long, with what effects, and the financial costs of operating the system.

Key Points Immigration detention is used worldwide by governments to facilitate immigration enforcement, but has negative impacts on detainees’ mental health. The use of immigration detention in the UK hit a high of around 32,000 in 2015. Numbers have been falling since then, with around 16,000 people entering detention in 2023. Around 1,800 people were in immigration detention on 30 June 2024. In mid-2024, the UK had an estimated detention capacity of around 2,200 beds, of which around 77% were occupied. In 2023, the Home Office detained 18 children for immigration-related purposes, down from around 1,100 in 2009. In 2023, 39% of immigration detainees were held for more than 28 days. Release on immigration bail – an alternative to detention where detainees are released into the community – increased from 2010 to 2021 but fell by 2023. In Q2 2024, the average daily cost to hold an individual in immigration detention was £122. In the financial year 2023-24, the Home Office issued 838 compensation payments for unlawful detention, totalling around £12 million.

Oxford, UK: Migration Observatory, University of Oxford, 2024. 18p.