Disability and poor health are preventing nearly half a million people who are close to retirement from working, a figure that will only increase as the state pension age (SPA) rises, an analysis by the TUC has concluded.
The research, which was published in August, found that employment rates for those approaching the current SPA were low, with just 54% of men aged between 60 and 64 and 62% of women aged between 56 and 60 in work.
The Government is gradually raising the SPA in the hope that people will work longer and alleviate the UK's pensions crisis.
Under the Pensions Act 2011, the SPA will rise to 66 for men and women by October 2020 and to 67 by April 2028.
However, the TUC has argued that its evidence shows that, rather than automatically increasing working lives, the reality will be that more older people who are unfit or disabled will find it difficult to find employment and will be caught in a new "limbo zone" of being too young for a pension and too old to work.
Nearly two in five of those approaching the SPA were economically inactive (defined as someone who had not sought work in the previous four weeks), with long-term sickness and disability cited as the main reason.
People formerly working in skilled trades, heavy industry and low-skilled jobs were most likely to be inactive, while managers and senior officials were far more likely to be inactive because of early retirement.
Nearly 100,000 more people were inactive because of long-term sickness and disability (470,325) than the number of those taking early retirement (375,368), it added.
The TUC's general secretary, Brendan Barber, said: "While more people are working past their state pension age, often as the only way to get a decent retirement income, a far greater number of older people are unable to work due to ill health or because they are trapped in long-term unemployment."
In separate research, the charity Macmillan Cancer Support has warned that the number of people aged 65 and over living with cancer in the UK is set to more than treble by 2040 - from 1.3 million in 2010 to 4.1 million.
According to the Macmillan-funded research by King's College London, nearly one in four older people will have had a cancer diagnosis in 2040, almost double the proportion in 20