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London's hidden population

Key points

  • Some of London's poorest and most vulnerable populations are invisible in the official statistics we use here.
  • For example, undocumented migrants may be destitute but are unlikely to be included in surveys or government administrative data.

The problem with reliance on government sources

The indicators on this site use official statistics collected through government sources. The data does not allow consideration of very local differences in London or of the differences within broad ethnic or national categories. Moreover, while official statistics can give a good picture of London life for most of its population, some groups are not covered at all.


The Integrated Household Survey 2014 published by the Office for National Statistics estimates that 2.6% of adults in London identify as gay, lesbian or bisexual. This is higher than any other UK region with the average at 1.6%. But it is lower than other estimates of around 7% and could reflect the discomfort felt by participants answering the question. Data from the National Survey of Sexual Attitudes and Lifestyles found that 5% to 8% of people aged 16-44 had at some point had a sexual experience with someone of the same sex.

Data is not routinely collected about sexuality, so this website does not show patterns of poverty among London's LGBT population. However, research suggests that LGBT people can experience significant discrimination and exclusion in relation to health, employment, training, crime and housing, which are all related to poverty.

Asylum Seekers

London School of Economics researchers estimated in 2007 that about 500,000 people in London had applied for UK asylum in the previous 15 years. Of these, about half had secured refugee status, making up about 3-4% of London's resident population.

In mid-2015, Home Office data shows 2,600 asylum seekers in London were in receipt of "section 95 support" - accommodation and/or financial support available to destitute individuals whilst their asylum claim is being processed. Section 95 is set at 70% of Income Support levels (for adults) so most asylum seekers are likely to fall well below the poverty line. Not everyone in the asylum system claims - or is eligible for - Section 95 support, so these figures underestimate the number of Londoners in the asylum system.

Undocumented migrants

Undocumented migrants
Undocumented migrants are people who do not have a legal UK immigration status. Most are refused asylum seekers who are unable/unwilling to return to their country of origin, but they also include people who have overstayed their visas, children of undocumented parents and (the smallest group) people who have entered the UK illegally. The last category will include very vulnerable Londoners such as victims of trafficking.

A 2005 Home Office research paper estimated that there were between 310,000 and 570,000 undocumented migrants in the UK in 2001. A 2009 report written by the London School of Economics for the Greater London Authority estimated that in 2007 the number of undocumented migrants in the UK was at least 533,000. It estimated that 380,000 of these people lived in London, representing about 5% of its population. Research by COMPAS at the University of Oxford (2010) estimated that there were 120,000 undocumented children in the UK, of whom about half were born in the UK.

A survey by the Home Office of illegally resident detainees found that most had lived for at least some time in London, and two-fifths had never spent any time outside the capital. Though this was based on a small sample, it seems likely that most undocumented migrants will have spent some time in London as it is the main port of arrival from overseas. As such, they add to the churning of London's population, especially in boroughs near the main airports.

Many undocumented migrants are likely to be in poverty, but are unlikely to be included in official figures. While it is not impossible for them to find work, such work is almost inevitably low paid. Without documentation, it is difficult to get a bank account, which itself is often a barrier to work. They are not entitled to benefits and are excluded from most services including social housing.


Institute for Public Policy Research (2006) Irregular Migration in the UK, An IPPR FactFile

Black, R., Collyer, M., Skeldon, R., Waddington, C (2005) A Survey of the Illegally Resident Population in Detention in the UK, University of Sussex Centre for Migration Research, Home Office

Sigona, N. & Hughes, V., "Being Children and undocumented in the UK: A Background paper", Working Paper No. 78, COMPAS, University of Oxford

Travers, T., Tunstall, R., Whitehead, C., Pruvot, S (2007) Population mobility and service provision, LSE

Datta, K (2007) Money matters: Exploring financial exclusion among low paid migrant workers in London, Queen Mary, University of London

Ian Gordon, I., Scanlon, K., Travers, T., Whitehead, C., (2009) Economic impact on the London and UK economy of an earned regularisation of irregular migrants to the UK, GLA

National Asylum Statistics, Home Office

Woodbridge, J (2005) Sizing the unauthorised (illegal) migrant population in the United Kingdom in 2001, Home Office

Office for National Statistics response to Freedom of Information Request for data on Illegal Immigrants

Blinder, S (2015) Migration to the UK: Asylum; The Migration Observatory

The National Survey of Sexual Attitudes and Lifestyles

Integrated Household Survey, Office for National Statistics

Indicator last updated: 21 January 2016