The ethnic minority population of Britain will almost double within the next 20 years to 10 million
Immigration is fuelling the biggest population growth since the post-war baby boom, according to a leading academic.
Oxford professor David Coleman says migration is leading to "quite radical ethnic changes".
These include the ethnic minority population of Britain almost doubling within the next 20 years to 10million.
Professor Coleman, an internationally-respected expert in demography, made his remarks to a Tory policy review group.
The session also heard a warning from the British Chambers of Commerce that young British workers are being "displaced" in the job market by migrants, including eastern Europeans.
BCC boss David Frost said it was "not tenable" for the young people to be left out of work in the long term.
Professor Coleman, who has faced demands from Student Action for Refugees to be sacked over his links to the Migrationwatch thinktank, said the population was growing by 0.6 per cent every year.
By far the most significant factor is migration - which has added an average of 204,000 extra people each year since 2004.
By 2051, the total population will have reached almost 70million, an increase of 10million.
Professor Coleman said the current rate of growth was the greatest since the 1940s and 1950s.
He added: "Quite radical ethnic changes are taking place."
As well as the growth in ethnic minorities, the white non-British population will also increase dramatically. Figures produced by Professor Coleman from Government estimates show it is expected to hit around 5million by 2026 - up by 3million.
The session, which will help to shape Tory immigration policy for the next election, heard that 700,000 eastern Europeans have moved to Britain since the expansion of the EU on May 1, 2004.
Mr Frost said the influx was leaving young Britons out of work.
Those from countries such as Poland often arrive with degrees but are willing to take nongraduate jobs. This leaves Britons without degrees with nowhere to turn.
He added: "There are now some concerns, wider economic concerns, coming through from the business community. There is a feeling that young white males are being displaced by migrants from eastern Europe, and that position is not tenable."
The scenario described by Mr Frost - who said seven out of ten company bosses do not want further expansion in the labour market from overseas - will set alarm bells ringing among Labour MPs, who fear a backlash from voters.
MPs have already warned that wages will be slashed because Poles are willing to work for less.
Professor Coleman questioned the Government's strategy of flooding the labour market with low- skilled workers. He said: "Employers are getting a very good deal from the present set-up.
"They benefit from the relatively low wages being paid to immigrant groups without having to bear the costs these low wages generate, such as access to housing.
"The taxpayer is subsidising the employers in picking up the bill."
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