Britain's population could hit 70 million in less than 50 years
Government adviser Lord Turner painted a stark picture of the potential impact on housing, employment and traffic congestion.
He said the South East would be hardest hit by such a surge. The current population is around 60 million and a 10 million increase would be 4 million more than previously estimated.
Lord Turner said ministers could not decide between attacking the Tories for playing the 'racist card' on immigration and launching a crackdown on illegal migrants.
He said: 'What always amazes me is we have piecemeal discussions which never consider: would you prefer a population of 60 or 70 million? It is an area that
Warning: Lord Turner depresses me. The Government itself varies between attacking the Tories for trying to play racist cards and suddenly swinging round on a sixpence to be as nasty and tight as it can towards asylum seekers. There is an incoherence about the debate.'
The extraordinary intervention by Lord Turner - who examined demographic changes when he headed the Government's Pensions Commission - is the latest from a senior figure on the failure of immigration policy.
Last month former minister Frank Field said Britain was suffering from an unprecedented influx of migrant workers and that MPs were living on borrowed time on the issue.
Lord Turner said the population would rise from 60million to 66million by the year 2050. But he predicted that if immigration went unchecked, the real figure would be 70million.
The former chairman of the Low Pay Commission said that selective skilled immigration was justified to help boost the economy and help fund pensions for the current workforce through increased tax payments.
But he warned that high levels of unskilled workers entering the country may have a short-term benefit but would ultimately damage the economy.
Lord Turner said: 'The undoubted winners from immigration are immigrants. High levels of immigration of unskilled people will be good for higher income people who will buy their coffees and their haircuts at a slightly lower price.
'The economic disbenefits are that high levels of unskilled immigration are bad for unskilled workers and I think to deny that is nonsense - it just flies in the face of all economic theory.
'We were aware on the Low Pay Commission that if immigration continues at high levels that could limit our ability to increase the minimum wage.
'On the other hand, the best form of immigration policy for our economy is almost certainly selective skilled immigration, but that has an ethical issue about cream-skimming the skills of underdeveloped countries.'
His comments follow those of Mr Field, who said anyone who questioned mass immigration was accused of 'playing the race card', which was just 'another way of closing down debate'.
Immigrant population ‘to be 70m by 2050’