A startling report has revealed that nearly one in 12 people living in London may be an illegal immigrant, with as many as 600,000 individuals residing in the capital without legal status.
The previously confidential study, commissioned by Thames Water, aimed to assess the "hidden" population using the utility company's services to better manage demand.
Conducted by Edge Analytics, the research combined academic estimates of illegal migrants in the UK with National Insurance data for non-EU nationals spanning nine years. The findings estimated London's "irregular" population ranges from 390,355 to 585,533, with a median figure of 487,944.
The study revealed that most illegal migrants initially entered the UK on work, study, or visitor visas but overstayed their permitted duration. Nationally, the report suggested there are over one million illegal migrants in the UK, with 60% concentrated in London.
Channel crossings on the rise
The data coincides with record-breaking levels of illegal Channel crossings. Over 1,000 migrants have already arrived in the UK by boat in 2025, marking the fastest start to the year on record for such crossings. On Tuesday, despite poor visibility, two small boats carrying 129 individuals were intercepted by Border Force vessels, bringing the year's total to 1,019 migrants across 18 boats.
The surge in crossings continues to put pressure on the government, with critics arguing the country has "lost control" of its borders. Shadow Home Secretary Chris Philp described the figures as "unacceptable" and called for reforms to prevent the misuse of human rights and asylum claims as a means to delay deportations.
Richard Tice, deputy leader of Reform UK, also weighed in, stating, "One in 12 people in London are here illegally, likely working illegally while using taxpayer-funded services. This situation is unacceptable and underscores the urgent need for border control."
Government crackdown on illegal work
Authorities have intensified efforts to tackle illegal working and exploitation. Between July and November, nearly 1,000 enforcement visits across London led to 770 arrests and 462 civil penalty referrals. Businesses hiring illegal workers face fines of up to £60,000 per worker.
The raids targeted car washes, nail bars, supermarkets, and construction sites—industries often linked to exploitative labor practices, including subminimum wages and unsafe conditions. A Home Office spokesperson emphasized the government’s commitment to dismantling criminal gangs facilitating illegal migration.
Minister for Border Security Angela Eagle MP highlighted the importance of clamping down on illegal working to safeguard individuals who are misled into believing they can live and work in the UK.
Calls for global partnerships
The Prime Minister has also indicated willingness to explore international agreements to curb illegal migration. Talks are reportedly underway with countries like Vietnam and Kurdistan to address the flow of migrants at its source, with the UK considering financial incentives to aid these efforts.
Despite these measures, critics argue that more robust actions are needed to restore control over the UK's immigration system. Last year, over 36,800 individuals crossed the English Channel in small boats, making it the deadliest year on record for such journeys.
Public responsibility
A senior Home Office official has also urged Britons to consider the role they play in sustaining illegal migration by using cash-only services such as nail bars and car washes, which can contribute to modern slavery and exploitation.
Thames Water, which commissioned the study, clarified that the report was based on independent analysis using public data and does not reflect its own conclusions.
As the government intensifies enforcement efforts, the report serves as a stark reminder of the ongoing challenges surrounding illegal migration and the need for coordinated action at both local and international levels. Photo: Gémes Sándor/SzomSzed, Wikimedia commons.