The number of people working beyond state pension age has almost doubled to 1.4 million in the past 20 years, according to official figures.
The Office for National Statistics (ONS) said the numbers were relatively stable until 2000 but then increased to a peak of 1.45 million in 2010.
A third of older workers were self-employed, compared with 13% of those below the state pension age, while older employees were twice as likely to be working part-time than be in full-time posts.
The ONS said those remaining in the labour market over state pension age worked fewer hours, possibly helped by the financial support of their state pension and other pension arrangements, allowing them to fit their work around other engagements.
Of the 1.4 million older workers above state pension age, 39% were men and 61% were women.
Around two-thirds of the men worked in jobs classed as higher skilled, such as property managers, marketing and sales directors, production managers and chief executives, but almost two-thirds of these women worked in lower skilled jobs.
Of all the jobs carried out by men, the two most common were farmers and taxi drivers, while for women the most common job was cleaning, followed by administration assistants, care workers and retail assistants.
The study showed that the number of older workers rose from 753,000 in 1993 to 1.4 million in 2011.
Dr Ros Altmann, director-general of Saga, said: "Many older people are increasingly choosing to stay at work, often part-time so that they ease more gently into retirement. If they feel fit and healthy and want more money, and are able to work, they are choosing to do so.
"Saga's research shows that many of our over-50s already want to work past 65. Around 71% would like to work part-time rather than retiring and in fact 7% are already working past the age of 70. This isn't just for the money - work satisfaction, feeling useful and the social benefits we gain from working were key reasons that people wanted to continue."