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Immigration Detention in the UK

02 May 2017

This briefing provides an overview of immigration detention in the UK. It discusses the size of the UK’s detention facilities, the number of detainees, the average duration of detention, and the detention of children.

  1. Key Points
    • The UK immigration detention estate is one of the largest in Europe. From 2009 until the end of 2016, between 2,500 and 3,500 migrants have been in detention at any given time.
    • In 2016 28,900 people entered immigration detention compared to approximately 32,400 in 2015.
    • The majority of immigration detainees are held for less than a month.
    • The single most common category of immigration detainees is people who have sought asylum in the UK at some point.
    • Over 1,000 children were detained for the purpose of immigration control in 2009, and this number was reduced to just under 130 in 2011. It rose to 242 in 2012, before falling to 71 in 2016.
    • In late 2016 the estimated average cost of detention was £86 per day.
  1. Understanding the Evidence

    Immigration detention refers to the government practice of detaining asylum seekers and other migrants for administrative purposes, typically to establish their identities, or to facilitate their immigration claims resolution and/or their removals. It is an administrative process rather than a criminal procedure.

    The reasons for which a migrant may be held in detention include: to effect removal; to establish a person’s identity or basis of claim; where there is reason to believe that the person will fail to comply with any conditions attached to the grant of temporary admission or release, i.e. a risk of absconding; where there is a risk of harm to the migrant or the public; and as part of the now-suspended detained fast-track (DFT) system (whereby asylum seekers could be detained if their claims appeared capable of being decided quickly). There are also occasions when the reasons for a migrant’s detention change while he or she is already being held in detention.

    Border officials in the UK may detain migrants: on arrival; upon presentation to an immigration office within the country; during a check-in with immigration officials; once a decision to remove has been issued; and after a prison sentence or following arrest by a police officer.

    The publicly available data on immigration detention chiefly originate in publications released by the Home Office and Her Majesty’s Inspectorate of Prisons (HMIP). Data and information from non-governmental organisations’ reports, Hansard texts of Parliamentary debates and formal questions and scholarly articles supplement this information.

The UK’s immigration detention facilities are among the largest in Europe: between 2,000 and 3,500 migrants are detained at any given time

The UK has one of the largest networks of immigration detention facilities in Europe. After the re-purposing of the Morton Hall prison as an immigration removal centre (IRC) in June 2011 and the opening of a short term holding facility at Larne House in Northern Ireland in July 2011, UK detention capacity expanded to approximately 3,500 places. As shown in Figure 1, over the past years there have been between 2,000 and 3,500 migrants detained at any given time. As a snapshot example, there were approximately 3,500 non-citizen detainees in UK facilities in any given time between September 2014 and September 2015. By December 2015 the number of people detained under Immigration Act Powers decreased to approximately 2,607, a change that the Home Office notes “may be partially attributable to the closure of the Dover IRC in October 2015 and changes to the detained fast track asylum process”. Although 2016 saw a slight increase to just over 2,700 people, this was still relatively low as compared with the previous two years

Figure 1

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Approximately 28,900 migrants entered detention in the UK in 2016

Approximately 28,900 migrants entered detention under Immigration Act powers in 2016, compared to 32,400 in 2015 (UK Home Office 2016). These statistics do not include people detained in police cells, Prison Service establishments, short term holding rooms at ports and airports (for less than 24 hours), and those detained under both criminal and immigration powers and their dependents. Immigration detainees are held in Immigration Removal Centres (IRCs), Residential and Non Residential Short Term Holding Facilities (STHFs), and Holding Rooms either based at or near ports of entry and reporting centres.

A large majority of people entering detention are male. In 2016 24,814 males and 4,094 females entered detention

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Over half of immigration detainees are held for less than two months

In Q4 2016, about 81% of total immigration detainees leaving detention had been held for less than two months (Figure 2). It is also not uncommon for detention to span two to four months. A small but consistent minority of detainees – about 2% – are held for between 6 and 12 months, and an additional 1% held for more than a year.

Figure 2

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The most common category of immigration detention is people who have sought asylum in the UK at some point in their immigration adjudication processes

There are numerous categories of people who are detained under Immigration Act powers, and these categories can overlap. For example, new arrivals may be detained awaiting examination by an immigration officer to determine their right to entry; new arrivals who have been refused permission to enter the UK and are awaiting removal may also be detained; those who have either failed to leave the UK on expiry of their visas (so-called overstayers), have not complied with the terms of their visas, or have attained their visas by deception, may be detained; and undocumented persons found in the UK can be detained pending a decision on whether they are to be removed or pending arrangements for their removal.

The largest category of immigration detainees is persons who have sought asylum at some stage during their immigration processes. In 2016, asylum detainees accounted for about 46% of people entering detention (UK Home Office 2017).

The immigration detainee population also includes foreign national offenders (FNOs), some of whom apply for asylum while in prison. Since April 2006, the UK Government has prioritised the removal of FNOs. As of 1 August 2008, with the introduction of the UK Borders Act 2007, all FNOs who have been sentenced to a period of imprisonment of 12 months or more are subject to automatic deportation from the UK unless they fall within one of the Act’s six exceptions. Prior to removal, FNOs who do not qualify for an exception remain in prison under immigration powers and are not counted in official detention estate statistics. Since 2009, more than 4,000 FNOs have been deported annually. (See our briefing on ‘Deportations, Removals and Voluntary Departures from the UK’). As of Q4 2016, foreign national offenders were detained for an average of 118 days before deportation (Home Office 2017b).

The policy primer on ‘Immigration Detention: Policy Challenges’ provides more context, explanation and analysis of foreign national offenders and asylum seekers in UK immigration detention.

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Detention of children in 2016 was much lower than the 2009 levels

Throughout the 1990s, the Home Office rarely detained families with children. However, non-governmental organisations and other groups estimate the number of children detained with their families to have been up to 2,000 per annum between 2005 and 2009 (Crawley and Lester 2005, Sankey et al. 2010). Home Office statistics suggest that more than 1,100 children entered detention in 2009. This number fell to 436 in 2010 and to 127 in 2011 (Figure 7). In 2012 and 2013 the numbers increased to over 200 annually.  In 2015, 163 children entered detention, and this number fell by more than half in 2016, where 71 children entered detention.

Figure 3

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The financial costs of immigration detention

In answer to a 2007 request made under the Freedom of Information Act, the Home Office revealed that in 2005/6 the weekly cost per detainee ranged from £511 (Lindholme IRC) to £1,344 (Colnbrook IRC).
As of Q4 2016, the government reported the average cost per day to hold an individual in immigration detention at £86 (Home Office 2017b).

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Evidence gaps and limitations

Some gaps and limitations in the data remain. For example, it is often difficult to track individual trajectories of detention, release and re-detention through the statistics because they are presented as separate numbers of occurrences. It is important to supplement Home Office data with NGO tracking. There is also a deficit in information about the nature of discretionary decision-making by Home Office officials and judicial actors on when to arrest and detain, and when to release persons from detention; this information would go some way towards illuminating the meanings of the official statistics.  Such evidence gaps and limitations are important in discussions about how to access immigration detainees and provide them with services such as translation and visits.

There is a lack of clarity regarding the precise number of detention facilities, because of definition issues and recent changes.

As of January 2015, there were 11 IRCs, 4 RSTHFs, 1 NRSTHF, 1 pre-departure accommodation (for families), 19 Holding rooms at ports and 11 at reporting centres. Except for 4 IRCs that are managed by the Prison Service, the Home Office has outsourced the management of its detention facilities to private firms – Mitie, GEO, G4S and Serco. The contract for managing the Holding rooms, the NRSTHF and two of the four RSTHFs passed to Reliance (now Tascor) in 2011. Immigration detainees may also be detained in prisons and there is currently capacity for 600 detainees under a service level agreement with the National Offender Management Service.
Two of the IRCs have since closed; IRC Haslar and IRC Dover which were closed later in 2015. Cedars pre-departure accommodation was closed in 2016, but is due to re-open at Tinsley. Further updates to these numbers can be made as information becomes available.


With thanks to Mary Bosworth, Emma Kaufman, and officials at the Home Office.


Related Material


  1. Media Coverage
    • Independent (26 Oct 2016)

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