Representative image showing an aerial view of London
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According to a confidential report, about 5,85,000 illegal migrants which makes approximately one in 12 people amongst the population, have been residing in London.
The figure has raised concern over the inability to secure British borders.
According to a report by The Telegraph which quoted a study commissioned by Thames Water, United Kingdom has an estimate of over one million illegal migrants in the country of which 60 per cent happen to be in London.
According to the study, these migrants who arrived in UK to work, study or on visiting visas, are now tagged 'illegal migrants' for they have been overstaying in the country.
Since the data is from 2017, the figures of the number of the migrants could be an underestimate.
According to The Telegraph, the Home Office on Tuesday confirmed that in 2025, about 1,000 migrants have crossed the country's borders, with 38,816 in 2024 being the highest ever total record of illegal immigrants in the UK.
Shadow Home Secretary Chris Philp said that the figures mentioned in the study are 'deeply alarming'.
According to the publication's report, Chris said, "Having lost control of illegal immigration over the Channel, the Labour Government must now urgently start deporting far more illegal immigrants."
He further added, "It is totally unacceptable to have these numbers of illegal immigrants in the UK. The law needs to be looked at so that spurious human rights, modern slavery and asylum claims cannot be used to delay or prevent removals of illegal immigrants."
Alp Mehmet, Chairman of think tank Migration said, "A population underestimate on this scale has colossal implications for utility and local authority planning. Utilities, housing, the NHS, GP surgeries and schools will all come under severe pressure, further risking community cohesion."
According to The Telegraph, Reform UK's deputy leader Richard Tice said, "One in 12 people in London are here illegally, probably working illegally using taxpayer-funded public infrastructure and services. It is totally unacceptable. It’s another reason why we need to properly control our borders."
The cited study is based on academic estimates of illegal migrants from Pew Research Center in the US, the London School of Economics, Office for National Statistics data and other research as well.
According to the study, if covered, the areas outside London including - Henley, Guildford, Reading, Swindon and Newbury - the illegal migrants would amount to 6,23,351.
According to The Telegraph, former director general of immigration enforcement David Wood in 2019 had said that the figures of illegal migration were approximately around 1,50,000 a year.
The study also said that about 1,65,000 legal migrants are working illegally in the UK who weren't in the formal figure count for they been having staying officially and legally in the country.
"This government is strengthening global partnerships and rooting out the criminal gangs who profit from small boat crossings which threaten lives. We have also removed 16,400 illegal migrants in just six months, the highest figure in half a decade, making it clear that those who arrive illegally will be returned," a spokesperson of the Home Office said.