Immigrants will be the main force in a 10 million rise in Britain’s ballooning population within the next 25 years, equivalent to a city bigger than London.
The Office for National Statistics said the population would rise by 9.6 million by 2037, reaching 73.3 million people.
About 60 per cent of the increase, equal to 5.8 million people, is linked to immigration, either from new arrivals or people having children when they settle.
The figures will put David Cameron’s pledge to reduce net migration to “tens of thousands” by the end of this Parliament under growing scrutiny. The ONS said Britain can expect 165,000 immigrants a year until 2037.
It comes amid growing concerns about a new wave of migrants from Bulgaria and Romania next year, when restrictions are being lifted.
The new wave of migration could lead to 50,000 people a year moving to this country. Observers fear Britain is facing an “unsustainable” influx of migrants.
Sir Andrew Green, chairman of Migration Watch UK, said the figures underlined the need to have a net migration target and stick to it.
“These latest projections confirm that we are still on course for a substantial increase in population,” he said.
“By the end of the next parliament, the population will have increased by three million, the equivalent of Birmingham, Liverpool, Manchester, Glasgow, Cardiff and Aberdeen.”
The ONS said that by 2037 an additional 4.2 million immigrants would come to Britain. The children of immigrants would account for a further 1.6 million rise in the population.
The number of primary schoolchildren will rise by 13 per cent to reach 5.7 million by mid-2037.
Over the same period, the number of secondary school age children will rise by 10 per cent to 4.1 million.
Official figures show that almost one in five pupils in primary education now speak another language in home, with native English speakers in a minority in several inner London areas.
Leading academics warn that the education system is at crisis point because of the lack of primary school places.
Paul Vickers, the head of government policy at the ONS, said: “The whole purpose of producing the research is to inform government policy and resource decisions. One of the major issues is the allocation of schools places.”
Earlier this week a review commissioned by the government found that migrants were filling a fifth of jobs in key industries because of a lack of skilled British graduates.
The review, published by the Department for Business Innovation and Skills, found that companies were forced to rely on foreign-born workers in a range of “strategically important” areas as children shun maths and science.
David Cameron said last week that Britain must “say no” to Eastern European workers by making young people more able and willing to compete with immigrants.
The Prime Minister said that in factories across the country up to half of the workforce came from Eastern European countries such as Poland and Lithuania.
He said it was a “cruel fact” that a generation of young Britons could be “left behind” and fail to share in the benefits of the economic recovery because they lacked the skills to secure a job.
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