One in 10 pensioners is either working or looking for a job, official figures have shown.
Some 9.2 million residents of England and Wales were aged 65 and over in 2011, an increase of nearly one million from a decade earlier, according to data from the latest census.
Ten per cent of them were economically active, defined as either being in employment or seeking work, including 158,000 people aged 75 or over, showed analysis by the Office for National Statistics (ONS).
The proportion of older people aged between 65 and 74 who were still economically active nearly doubled in 10 years, rising from 8.7% in 2001 to 16% in 2011 - an increase of 413,000 people.
The ONS said increased life expectancy, the removal of compulsory retirement age and the economic pressures from rising living costs were key factors behind the increase in working pensioners.
"This trend is likely to continue, as the age for women's state pension eligibility increases to align with men by 2018," it added.
The ONS report found 14% of pensioners living in households in England and Wales were providing unpaid care in 2011, compared with 12% in 2001. This included 497,000 over 65s (5.6%) who were providing at least 50 hours of unpaid care a week - an increase from 341,000 (4.3%) in 2001.
The ONS added: "This increase in unpaid care provision by older people may relate to providing care for a spouse or elderly parent in the home, as life expectancy continues to rise. There is also growing evidence of the adverse impact on health for those providing unpaid care."
The report also found the proportion of divorced people aged 65 and over almost doubled from 5.2% in 2001 to 8.7% in 2011. This compared with a smaller increase from 8.2% to 9% for the general population.
In 2011, 5.2 million pensioners were living as a couple, compared with 4.3 million in 2001, the ONS said. Just under a third (31%) of people aged 65 and over were living alone in 2011 - a fall from from 34% in 2001.