'Global upheaval' will make Britain home to 69m by 2050

Immigration will be responsible for around three-quarters of the 9 million increase – the equivalent of 150,000 new arrivals a year.

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The UN's population division says the changes will be part of a global upheaval without parallel in human history.

The world's population will grow by 2.5billion over the next four decades to reach about 9.2billion by 2050.

Almost all the increase – the equivalent of the entire global population in 1950 – will happen in Africa, Asia and the Middle East.

Tens of millions of people from these areas will migrate to Europe and America, with 2.2million new arrivals each year across the developed world.

Yet the native populations of most developed countries will either stagnate or decline, the UN predicts.

Nor will all Western countries be as much of a magnet for migrants as the UK, the report says.

While Britain's overall population surges, Bulgaria's will fall by 35 per cent by 2050.

Ukraine's will plummet by 33 per cent, Russia's by a quarter and Poland's by a fifth.

There will also be 10 per cent fewer Germans and seven per cent fewer Italians.

The prediction will increase concern that Britain is taking a disproportionately large number of migrants, attracted by the Government's "open door" policies.

Migrants are also seeking to benefit from the availability of jobs here, as well as a relatively generous benefits system.

All have been significant factors in migrants adding around 1.5m to the UK population since Labour came to power in 1997.

In the past two years alone, there have been around 700,000 new arrivals from Eastern Europe – the vast majority of them Poles.

Shadow Home Secretary David Davis said last night: "These stark figures illustrate why the Labour Government needs to get a grip on our immigration system, and properly take into account the impact of migration on schools, hospitals and other public services."

"Migration can be of benefit to Britain, but only if it is properly managed."

Between 1970 and 1980, the developed world took about a million migrants a year from poor countries.

But the UN says immigration will run at more than twice that level over the next 43 years.

It will approach 2.3million every year from now until 2050. Of these, some 400,000 a year will come from Africa and about 1.2million will emigrate from Asia.

The UN says that India will have the largest population in the world by 2050, totalling almost 1.7 billion people.

There will be 292million Pakistanis, giving their country the fifth biggest population.

Nigeria will have 289million people – making it the world's sixth most populous country – and Uganda's population will rise to 93million, comfortably exceeding the totals in both its larger neighbours, Kenya and Tanzania