The number of active workers aged 50 and over has reached a record high of 10.39m according to data published by the Office for National Statistics (ONS).
Meanwhile the number of workers who define themselves as retired before the age of 65 has fallen to 1.15m, a record low.
Analysis of the figures by Aviva showed the number of older workers is rising by about 2m every decade.
When records began in 1992 workers over the age of 50 represented about one-in-five in the workforce – 6m people. In the coming decade, Aviva predicted this cohort would represent one-in-three.
Alistair McQueen, head of savings and retirement at Aviva, said: "Britain’s older workers are rising to the challenge of a longer working life.
"When the long-standing state pension ages of 60 for women and 65 for men were introduced in the 1940s we could typically look forward to 10 years of retirement. Today, expected retirement time has all but doubled and is now closer to 20 years.
"Working later in life is one of the most fundamental ways of paying for a longer retirement. Employers now face the challenge of supporting a fuller working life for all. Age must be no barrier to contributing to the UK economy."
Previous analysis from Aviva indicated early retirement would disappear by 2035 due to the decreasing number of people retiring before the age of 65.
Stephen Lowe, group communications director at Just, said the continued employment growth for people aged between 50 and 64 was not a surprise, given the state pension age for women has been pushed back.
He said: "Now that men’s state pension age is set to change, we should see a pick-up in employment among the older age group too."
In July the Department for Work & Pensions decided the increase in the state pension age should be brought forward to 68 between 2037 and 2039 because of increases in life expectancy.
Under the current plans the state pension age will increase to 68 between 2044 and 2046.
The change will leave 7.6m people £10,000 worse off, according to analysis by the House of Commons Library.
The ONS figures also showed the level of employment in the UK has continued its rise, leading to a record-high employment rate of 75.4 per cent in the three months to February 2018.
The growth in the number of people in employment was driven by an increase of 103,000 in the number of employees, with the number of self-employed shrinking by 18,000 on the previous quarter.
Malcolm Mclean, senior consultant at Barnett Waddingham, said this is good news for savings.
He said: "More people in employment means more people have the opportunity to benefit from auto-enrolment.
"We must continue to bang the drum for this most worthy of initiatives.
"Low earners, in particular, should be encouraged to see the need for longer term saving - not to be put off by this year’s and next year’s increases in the minimum contribution rates."