According to Professor David Coleman, a leading population expert, failure to deal with the influx of foreign workers would 'change national identity'.
The Oxford University professor's warnings have come as the Migration Advisory Board prepares to reveal its recommendation for the Government's proposed cap on immigrants from outside the EU, the Daily Mail reports.
If immigration stays at its long-term rate of around 180,000 a year, the white British-born population would decline from the current total of 80 percent to just 59 percent in 2051, analysis of figures from the Office of National Statistics shows.
By then white immigrants would reportedly have more than doubled from 4 to 10 percent of the total, while the ethnic minority population would have risen from 16 to 31 percent. If the trend continued, the white British population, defined as English, Welsh, Scottish and Irish-born citizens, would become the minority after about 2066, the paper said.
The Government has vowed to slash the level of net immigration after a decade of open borders under Labour. Today the Migration Advisory Board would reportedly suggest a level for the cap, following complaints from businesses that the plans are hampering their ability to bring in key staff.
However, Professor Coleman believes that even if the Coalition gets net immigration down to 80,000 a year, Britons would be outnumbered by 2080.
In an article for Prospect magazine, he writes: "The 50 percent benchmark has no special demographic significance, but it would have a considerable psychological and political impact."
"The transition to a "majority minority" population, whenever it happens, would represent an enormous change to national identity - cultural, political, economic and religious," he added.
He further warned that the relative youthfulness of the immigrant population means that the 50 percent milestone will be passed much quicker among 'schoolchildren, students and young workers'.
The ethnic minority population expanded by almost two million between 2001 and 2007, from 13 percent to nearly 16 percent of the total. Immigration accounted for 57 percent of population growth in this time, and foreign-born mothers now account for a quarter of births in England and Wales, the paper added.
Both Leicester and Birmingham are expected to become 'majority minority' during the 2020s. Two London boroughs were already majority non-white in 2001. (ANI)