The population of the United Kingdom is to top 70 million in the next 12 years, according to projections from the Office for National Statistics.
Migration and children born to new arrivals will help swell the population by just under 10 million over 25 years, according to the figures.
The figures also predict a rapidly ageing society, with one in 12 people aged over 80 by 2039.
"Growth will be at a faster rate than we have seen previously, largely due to the direct impact of international migration and the indirect impact of immigration," said Guy Goodwin, ONS director of social analysis.
"Despite this, the population will also be older as those born shortly after World War Two and during the 1960s \’baby boom\’ reach the oldest and pensionable ages respectively."
"The number of people of age 80 or over will more than double over the next 25 years."
If current trends continue, Britain would overtake Germany to become Europe\’s most populous country by 2050, according to experts.
The data assume that overall 200,000 more people a year will enter the country than leave it on average.
Immigration minister James Brokenshire said the figures showed the government should continue work to curb migration to Britain.
"The projections underline the importance of controlling immigration and show that the Government is right to continue its work to reduce net migration to more sustainable levels," Brokenshire said.
"We know that uncontrolled, mass migration makes it difficult to maintain social cohesion and puts pressure on public services."
In all over the next 25 years, Britain is expected to see a 15 percent growth in its population, far outstripping the European Union which is seen having 3 percent growth.