The number of people aged 80 and over in the UK will double to 6 million by 2037, according to official projections
The Office of National Statistics said this increase means one in every twelve people is projected to be aged 80 and over in 24 years time.
Over the same period the number of people of state pension sage is projected to increase by 31% from 12.3 million in mid-2012 to 16.1 million by mid-2037. This reflects the higher number of people who were born in the 1960s 'baby boom' reaching state pension age.
But while the number of people aged 90 and over is expected to triple, the ONS figures assume mortality rates for women aged 83 and over, and for men aged 86 and over, will worsen in future years.
Commenting on the figures, Matthew Fletcher, a consultant at actuaries Towers Watson said: 'The ONS now assumes that pensioners in their 80s have slightly less chance of living into their 90s and beyond than it thought they did two years ago.
'For example, it used to assume that 44.5% of men aged 80 in mid-2013 would live to 90, but now put this figure at 43.3%. However, younger pensioners are assumed to have more chance of living to 80 in the first place.'
The ONS also said that it expected the number of people of working age to rise by 12% from 39.4 million in mid-2012 to 44.2 million by mid-2037.
It noted that, in mid-2012, there were 0.3 million more people of state pension age than children aged under 16, but pensioners are expected to outnumber under-16s by 3.1 million by 2037.