BRITAIN’s illegal immigrant population is rising by 70,000 per year in a national “scandal” – a think tank has declared.

Migration Watch accused the Home Office of “serious failure” at the border and urged ministers to reconsider the introduction of ID cards to end the chaos.

It said the controversy sparked by the Windrush affair had “masked” the Government’s inability to remove hundreds of thousands of people who have no right to be in the country.

Migration Watch claimed around 83,000 foreigners overstay their visa every year.

There are also nearly 12,850 detected ‘clandestine’ arrivals or lorry drops and 8,500 failed asylum seekers who do not depart – a total of 105,000.

But the think tank claimed that only an average of 32,500 illegal immigrants are removed from Britain or head home voluntarily – leaving a difference of more than 70,000.

The 70,000 is almost equivalent in size to entire full-time British Army. Migration Watch chair Lord Green stormed: “The scale of illegal immigration to Britain is a scandal that has gone on for too long.

“It undermines public acceptance of genuine refugees and is damaging to community relations generally."

He added: “The government must not cave in to opposition attempts to ‘weaponise’ Windrush against legitimate and effective measures to tackle overstaying.”

Former Immigration Enforcement chief David Wood last year said there were an estimated one million illegal immigrants who were unlikely to ever be removed from Britain.

The Home Office said it “did not recognise” the Migration Watch estimates - but didn’t deny them. A spokesman said: “By its very nature, it is not possible to estimate with any confidence the size of the illegal population.”

A scathing report on the Government’s customs ‘Exit Checks’ in March found there were no departure records for 600,000 people whose visa or ‘leave to remain’ expired between 2015 and 2017.

At the time the Home Office considered that at least some of these individuals were likely to be “probable overstayers”.