The UK's population is going to swell by almost 10 million people in the next 25 years, taking us to a total of 74.3m by the middle of 2039.
The figures, projected by the Office for National Statistics, suggest that by 2027 the UK will reach the 70 million point. Net migration is expected to account for 51 per cent of the total increase, while a "natural increase" will account for 49 per cent of the growth.
The ONS has had to revise its forecast for growth over the next decade upwards to 4.4m from the 2012 estimate, which was around 250,000 lower.
However the population is projected to continue ageing, with the median age rising from 40 years in 2014 to 40.9 years in mid-2024 and 42.9 by mid-2039, by which point one in 12 people will be 80-plus.
England's population will grow by 7.5 per cent by the middle of 2024 - the fastest rate across the union. Northern Ireland is forecast to grow by 5.3 per cent, while Scotland and Wales will grow by 3.1 per cent, the ONS said.