The retirement income specialist found the majority of these people were working to supplement their income although some did voluntary work.
Some 44 per cent were working to earn money, 31 per cent liked the social interaction and 21 per cent wanted something to do with their time.
The average time spent working in retirement was 5.5 hours per week. Some 38 per cent worked 1-2 hours, 29 per cent worked 3-5 hours and 33 per cent worked more than six hours.
However, six per cent of retirees were running their own businesses and five per cent were working as a non-executive director.
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Aston Goodey from MGM Advantage said retirement was becoming a 'part-time pursuit' for many.
He said: "With people living longer, the experience of retirement is changing dramatically. There are significant numbers of people who no longer fully retire at a set date and are looking into alternative working patterns, sometimes part-time work or non-executive directorships and consultancy.
"What is worrying is that for many people retirement is a part-time pursuit because they need to supplement their income."
Research by Scottish Widows in May found that the average amounts retirees needed per year to sustain a comfortable lifestyle was £25,200. This requires people to have saved a pension pot of over £600,000 during their working life.

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