Between mid-2022 and mid-2023, the combined population of England, Scotland, Wales, and Northern Ireland increased from an expected 67.6 million to 68.3 million.
According to the ONS, the additional 662,400 individuals represented a 1% rise.
The increase in numbers is the highest since similar data were first kept in 1971.
“Net international migration was the main contributor to population increase for all four countries of the UK in the year to mid-2023,” according to the ONS.
The current estimate for net international migration over this era is 677,300.
Officials did, however, issue a warning, stating that while the ONS works to enhance its data, all predictions were probably going to be changed within the next year.
The difference between births and deaths, or the natural change in population, was 16,300. The ONS had previously predicted that a negative reading would not happen until the middle of the 1930s.
The ONS claimed that this was the first instance of a negative “natural change” in the population since 1976, with the exception of 2020 during the COVID epidemic; however, that year’s data was for the calendar year.