As many as one in 12 people in London is an illegal immigrant, a shock report has claimed.

The previously confidential study commissioned by Thames Water found that the 'irregular' population of the capital could be more than half a million.

It aimed to quantify the 'hidden' users of the utility firm's services to better meet demand.

Researchers at Edge Analytics used academic estimates of illegal migrants nationally as well as National Insurance registrations for non-EU foreign nationals over a nine-year period to estimate the numbers in each London borough.

The study produced a range of figures from 390,355 at the lowest to 585,533 at the highest with a median figure of 487,944.

It suggested most illegal migrants arrived in the UK on work, study or visitor visas then overstayed.

The report obtained by The Telegraph claimed there is estimated to be more than one million illegal migrants in the UK, with 60 per cent of them in England's capital. 

Many illegal migrants arrive in the UK on work, study or visitor visas and then overstay the limit.

The Home Office doesn't publish any comprehensive data estimating the number of illegal migrants in the UK.

It has only published figures on the number of illegal Channel migrants reaching the UK since 2018.

Shadow Home Secretary Chris Philp 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, told The Telegraph: '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.'

Yesterday it was reported that more than 1,000 migrants have crossed the English Channel in small boats so far this year, in a new record laying bare how Sir Keir Starmer is struggling to cope with the crisis.

Two dinghies carrying 129 people were spotted by Border Force vessels on Tuesday despite poor visibility - taking the provisional total for 2025 to date to 1,019 in 18 boats.

This means it has only taken 21 days this year for crossings to reach 1,000 - the quickest time on record.

Those on board were brought into the Port of Dover, Kent, after being taken onboard Border Force catamarans mid-Channel.

The latest numbers add pressure on the PM as he struggles to get to grips with the issue.

In November, Sir Keir said the government was prepared to pay governments in Vietnam, Kurdistan and Turkey to help stop the flow of illegal migrants to Britain.

The Prime Minister said he was prepared to look at 'anything' that would help slow the wave of migrants crossing the Channel illegally.

He declined to comment directly on reports the Government is in advanced talks with administrations in Kurdistan and Vietnam over deals in which Britain would pay them to help stop migrants heading for the UK.

But he indicated he was not against the principle of paying third countries to help tackle the Channel migrant crisis.

'Anything else we can do to stop people leaving in the first place is the right thing,' he said.

However, the Tories said the government had 'lost control' of Britain's borders.

Last year, 36,816 people successfully crossed the busy shipping strait during the deadliest year on record for small boat migrants.

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.'

Home Office sources told The Telegraph the underlying data were out of date and there was no officially recognised way of measuring how many illegal migrants are in Britain.

On Monday a major rescue operation was launched to save 84 migrants crammed into one dinghy after it stranded on a sand bank as they tried to cross the English Channel.

The French coastguard was alerted after witnesses on a a beach saw the overloaded inflatable attempting to make the crossing to the UK.

A French customs vessel nearby was sent to the area to monitor the dinghy off Walde, near Calais.

After arriving, the crew reported the dinghy had stranded on a sandbank but they could not get close enough to assist as the water was too shallow.

The stranded migrants also made a distress call to the French authorities.

A navy air sea rescue helicopter was scrambled as well as another boat to help with the rescue as the tide began to rise.

A total of 22 people isolated by the tide were recovered from the sandbank and transferred to the customs boat.

The remaining 62 on board the dinghy, were able to carry on trying to reach the UK but they too put out a second distress signal.

They rescue tug Abeille Normandie, chartered by the French Navy, went to assist and picked up the 62 people remaining on board the boat before dropping them off at the French port of Boulogne-sur-Mer where they were all taken care of by the rescue services on land.

 A Thames Water spokesman said: '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.'

Hundreds of people were arrested last month as the government cracks down on illegal working at car washes, nail bars and supermarkets in London.

Nearly 1,000 enforcement visits have been carried out by the Home Office's Immigration Enforcement team across the capital between July and November.

In that time 996 visits resulted in 770 arrests and 462 premises receiving civil penalty notice referrals. Employers could face a fine of up to £60,000 per worker if found guilty.

During one recent visit to a hotel in Kensington, six agency staff were arrested with five on suspicion of illegal working and one identified as having overstayed their visa.

Minister for border security and asylum, Dame Angela Eagle MP said: 'Dismantling criminal gangs and restoring order to our asylum system is a key part of our Plan for Change.

'That's exactly why we are clamping down on illegal working to prevent this abuse of our immigration system and safeguard those who are sold a false promise about their ability to live and work here.

'Since the election, arrests and enforcement visits have deliberately increased, demonstrating that we will not tolerate any hiding place from law enforcement.'

The raids had a focus on targeting car washes, nail bars, supermarkets and construction sites which were suspected of hiring illegal workers and subjecting them to squalid conditions and illegal working hours at below minimum wage.

It comes after a top Home Office official warned Britons using cash-only nail bars, barbers or car washes are 'feeding the problem' of illegal migration and could be creating more victims of slavery.