The U.K. population rose by 513,300 people to a record last year, with international migration accounting for two thirds of the increase.
As of June 2015, there were a 65.1 million people living in England, Wales, Scotland and Northern Ireland compared with 64.6 million a year earlier, the Office for National Statistics said on Thursday. The 0.8 percent increase is similar to the annual average seen over the last decade.
Net migration, the difference between people coming to the U.K. and those leaving, climbed to 335,635, and so-called natural growth — births minus deaths — accounted for 171,848. The U.K. prison population and the armed forces grew by 5,790.
The figures come on the day that Britain votes on its 43-year membership in the European Union. Pro-Brexit campaigners made immigration central to their case, arguing that EU freedom-of-movement rules mean Britain can only reduce “unsustainable” levels of immigration by leaving the bloc. The “Remain” campaign said quitting would inflict serious economic harm.
The population figures count only those intending to reside in Britain for at least 12 months. They exclude short-term migrants, a factor that explains why official estimates of migration are lower than the numbers registering for National Insurance numbers.
The latest figures show net migration is similar to the level seen in 2005, as immigration rose to 636,277 and emigration fell to 300,642. Natural growth was smaller than in previous years as the number deaths increased, partly due to flu outbreaks in early 2015, and births declined. The older population continues to grow, with 18 percent of all U.K. residents now age 65 and over.
Eighty-four percent of U.K. residents live in England, where the population rose by almost 500,000 to 54.8 million, the figures show. London, the U.K. capital, saw its population grow by 135,024 to 8.67 million. The populations of Scotland, Wales and Northern Ireland stood at 5.4 million, 3.1 million and 1.9 million, respectively.