The UK population could reach nearly 74 million by 2036, up from the latest estimate of 67 million, with net migration adding around six million people, figures suggest.

There could also be an additional one million people in the UK aged 85 and over during the next 15 years.

The data has been published by the Office for National Statistics (ONS) and assumes a level of long-term net international migration of 315,000 a year from mid-2028 onwards.

All the figures are projections, not predictions, because they are based on current and past trends.

The actual levels of future migration and population may be higher or lower, and will be “affected by policy changes as well as the impact of as yet unknown migrant behaviour patterns”, the ONS said.

The population of the UK is projected to grow from an estimated 67.0 million in mid-2021 to 73.7 million by mid-2036, an increase of around 6.6 million or 9.9%.

Over this period it is projected that 10.8 million people will be born, 10.3 million will die, 13.7 million will move long term to the UK while 7.6 million people will emigrate.

This means that of the projected 6.6 million increase, 0.5 million would come from a higher number of births than deaths, while 6.1 million would result from net international migration.

Commenting on the figures, James Robards of the ONS said: “Expert views and the latest data covering the last 10 years has led us to develop a long-term net migration assumption of 315,000 each year from year ending mid-2028 onwards.

“It is important to recognise that there is uncertainty in the provisional international migration estimates. Future migration will be affected by policy changes as well as the impact of as yet unknown migrant behavioural patterns in the future.

“Put simply, if migration comes down so will future projections.

“If net international migration were to be, say, 20% higher than our long-term assumption, then it would be 379,000 per year. If it were to be 20% lower than our assumption, then it would be 253,000 per year.

“That is why we call these projections and not forecasts. There is uncertainty and these differences would affect the total size of the population accordingly.”

The figures have been published on the same day the Government announced its latest plans to cut the number of people arriving legally in the country, including restrictions on foreign care workers bringing relatives to the UK and a rise in the minimum salary threshold for those on skilled worker visas.

Legal migration minister Tom Pursglove said the changes will make a “tangible difference” to migration levels and help the UK get to a “more sustainable place” on net migration.

Responding to the ONS population projections, he told the PA news agency: “It is right that we have a managed approach to migration – where we can meet skills needs within our own economy and within our domestic population we should be doing that.

“I think it’s fair to say that the Government is already acting in response to those sorts of figures and we’re going to see this package of measures through that we think will make a tangible difference in terms of bringing those numbers down and helping us to get to a more sustainable place when it comes to net migration.”

The latest projections suggest the UK population could hit 70 million by mid-2026 – a decade sooner than in figures published in 2022, which projected a date of mid-2036.

They also suggest the size of the UK population aged 85 and over could grow in the next 15 years from 1.6 million (2.5% of the total population) to 2.6 million (3.5%).

The demographic mix of the population is projected to continue tilting more towards older age groups.

People aged 75 and over could account for one in 10 of the total population by 2029 and one in nine by 2037 – the same year that people of pension age are projected to account for one in five.

International net migration is projected to fall over the next few years from a peak of around 670,000 in the 12 months to June 2023, before settling at 315,000 from 2028 onwards.

Former home secretary Suella Braverman described the projections as “too high”, writing on X, formerly known as Twitter: “Recent government measures will help a bit but they’re very late. We need a cap on overall numbers so we can hold government to account and fix this problem.”

Karl Williams, research director at the Centre for Policy Studies, a centre-right think tank, said: “Once again, ONS figures illustrate the failure of successive governments to take control of immigration and tackle the housing crisis.

“For decades, we have failed to build enough new homes to meet demand from those already living in the UK and record net migration has only exacerbated the problem.

“The Government needs to deliver on its promise to bring migration down and do more to tackle the country’s cavernous housing deficit by facilitating housebuilding right across the country – greenfield and brownfield, urban and rural, north and south.”

The total projected increase in the UK population over the next 25 years is proportionately less than that over the past 25 years.

From mid-1996 to mid-2021, the population grew by 8.9 million (15.3%), while from mid-2021 to mid-2046 it is projected to grow by 9.5 million (14.2%).

The ONS said it will continue to develop its population figures during 2024, taking into account the latest data on international migration, and will update its projections towards the end of the year.