The number of Britons aged 85 years and over is set to make up 4.9% of the total UK population by 2049, according to the latest data from the Office for National Statistics.
The number of over 85s is expected to double both in number and as a proportion of the total population.
In 2024 there were 1.75m people aged 85 years and older in the UK, making up 2.5% of the population.
The number of Britons of pensionable age is also expected to increase from 12.5m in 2024 to 15.3m by 2049.
The numbers are impacted by both increases in life expectancy and lower assumed birth rates, affecting the balance between older and younger cohorts.
David Brooks, head of policy at Broadstone, said the latest ONS figures are likely to raise questions about the long-term sustainability of the State Pension.
He said: “Debates on single-issue matters like the State Pension risk missing more important issues around an ageing population. In practice, current policy trends are steadily shifting more risk onto individuals, and particularly onto workers and younger generations, who are being asked to save more, work longer, and manage more uncertainty over much longer lives.
“From a pension’s perspective, the core issue is not how much is spent, but how risk is allocated across generations, and at what point in the life cycle. Decisions about defaults, retirement pathways and flexibility increasingly determine who bears longevity, investment and later life risk - yet those intergenerational consequences are rarely made explicit.”
He added that long-term health and care costs risk becoming an ‘intergenerational battleground’ if Government policy does not address how these risks are shared.