Britain's population is projected to increase by 9.7 million over the next 25 years from an estimated 64.6 million in mid-2014 to 74.3 million in mid-2039, according to the Office of National Statistics (ONS).
The increase, equivalent to the population of Sweden, would be comprised 51 percent of net immigration and 49 percent "natural increase", the difference between births and deaths.
The population of Germany, currently Europe's most populous nation with 81.1 million, is set to fall below Britain's by 2047, according to the combined projections of the two countries' official statistical agencies.
Immigration is likely to be a key issue when Britain votes on whether to remain in the European Union in a referendum planned by the end of 2017.
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If it decides to leave, Britain will no longer be bound by the bloc's rules on freedom of movement, which would likely have an effect on its population growth.
Britain's population is also expected to become older, with the average age rising from 40 years in 2014 to 42.9 by mid-2039.