Almost a million - 980,000 - retirees were in some form of employment between January and March of this year, compared to 883,000 in the first three months of 2011.
The figures, from the Office for National Statistics' Labour Market Survey, come at a time when pensioners' incomes have been squeezed by poor investment returns, low annuity rates and rising inflation.

Working later and longer: There are 100,000 more over 65s still in employment compared to two years ago.
He said: 'As that number [of people working after retirement] creeps towards one million, it is vital to encourage all those approaching retirement age to properly plan for stopping work so they can make the most of their precious pension savings and other assets.'
It also said this was the reason why the number of people claiming pension credit - which tops up the state pension for those on low incomes to around £142-a-week - fell by 147,000 to just under 2.5million.

ONS figures: Around 1.38million under 65s are retired, a fall on last year which the DWP shows the effect of the rising women's state pension age.
He said: 'Along the council tax credit, pension credit is the benefit that goes unclaimed most frequently by pensioners.
'Our research shows that more than one in five pensioners are missing out on benefits of £655-a-year on average, and as much as £3,500 in some cases.
'Many pensioners are struggling to make ends meet due to insufficient pension income and depressed savings returns.
'At the same time they are missing out by failing to claim the benefits they should be receiving, often to the tune of hundreds of pounds each year that could make a real difference to the quality of their lives.'
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