As many as one in 12 people living in London is an illegal migrant, a previously confidential report reveals.
The figures, which show as many as 585,000 illegal migrants are living in the capital, come from a study commissioned by Thames Water and were released through a Freedom of Information request.
It comes amid growing pressure on the government to cut illegal immigration, with around 1 million people believed to be in the UK illegally.
The report, obtained by the Telegraph, shows the majority of illegal migrants entered the country on visitor or work visas before overstaying the allotted time.
Official numbers have not been published by the Home Office.
Chris Philp, the shadow home secretary, described the reported figures as “deeply alarming.”
“Having lost control of illegal immigration over the Channel, the Labour government must now urgently start deporting far more illegal immigrants,” the Conservative said.
“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.”
Richard Tice, the deputy leader of Reform UK, 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 and welcome those who come here legally but thank those who are here illegally as we return them where they came from.”
More than 1,000 people have crossed the Channel on small boats in the first 23 days of 2025.
Chairman Migration Watch Alp Mehmet, 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.”