It suggests that only a minority of people will describe themselves as Christians within the next decade, for first time.
Meanwhile almost one in 10 under 25s in Britain is now a Muslim.
The proportion of young people who describe themselves as even nominal Christians has dropped below half for the first time.
Initial results from the 2011 census published last year showed that the total number of people in England and Wales who described themselves as Christian fell by 4.1 million – a decline of 10 per cent.
But new analysis from the Office for National Statistics shows that that figure was bolstered by 1.2 million foreign-born Christians, including Polish Catholics and evangelicals from countries such as Nigeria.
At the same time the number of Muslims in England and Wales surged by 75 per cent – boosted by almost 600,000 more foreign born followers of the Islamic faith.
While almost half of British Muslims are under the age of 25, almost a quarter of Christians are over 65.
The average age of a British Muslim is just 25, not far off half that of a British Christian.
Younger people also drove a shift away from religion altogether, with 6.4 million more people describing themselves as having no faith than 10 years earlier.