As many as one million illegal migrants could be living in the UK (Image: Getty)
Alarming figures have suggested one in 12 people living in London are illegal migrants.
The capital could be home to as many as 585,000 illegal migrants, heaping more pressure on the NHS, housing and schools.
The Home Office has never produced any formal figures.
But a new study – commissioned by Thames Water – tried to identify the “hidden” and “transient” users of their services to enable them to better meet demand.
It suggests most illegal migrants arrived in the UK on work, study or visitor visas and then overstayed, the Telegraph said.
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Keir Starmer has been given a stark warning over the scale of illegal migration (Image: Getty)
As many as one million illegal migrants could be living in the whole of the UK.
Shadow Home Secretary Chris Philp branded the figures “deeply alarming”.
He said: “Having lost control of illegal immigration over the Channel, the Labour Government must now urgently start deporting far more illegal immigrants.
“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 the Migration Watch think tank, 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.”
Deputy Reform UK leader 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.”
Experts at Leeds University and Edge Analytics examined academic estimates of illegal migrants nationally including the respected Pew Research Center in the US, London School of Economics (LSE), Office for National Statistics data and other research.
It then used National Insurance registrations for non-EU foreign nationals over a nine-year period to estimate the number of “irregular” migrants in each London borough.
The study estimated that as many as 585,533 illegal migrants could be living in the capital. The lowest estimate put it at 390,355 illegal, with a median figure of 487,944.
A Thames Water spokesman said: “Water companies have a regulatory obligation to undertake a ‘water balance’, which includes understanding how much water our customers use on a per-person basis, and how it is distributed across our supply area.
“Analysis to estimate ‘hidden and transient’ populations is carried out by an independent firm of consultants, who draw from publicly available sources including census, surveys, and published academic research.
“Thames Water played no part in the writing of the report and the conclusions drawn are those of the independent firm that carried out the research.”
A Home Office spokesman said: “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.”