One in five UK workers (19%) believe they will never be able to afford to retire, according to HSBC's global Future of Retirement report, which surveyed 16,000 people in 15 countries.
The findings reveal that those living alone are among those most likely to have to continue working, with 36% of those who are divorced or separated expecting to work indefinitely, compared to just 20% globally. Similarly, 31% of those who are widowed also said they would have to work on, compared to 23% globally.
In the UK, two fifths of retired people surveyed (39%) said that they had not prepared adequately or at all for a comfortable retirement, with 35% of those people only realising they were underprepared after retiring.
Almost half (44%) of those who said they hadn't prepared adequately are "resigned to the idea that they will just never be able to make up their shortfall," HSBC said. A further half (49%) of people said they were unable to realise their retirement dreams because they had less money than they envisaged.
Globally, 27% of people said they would start a business in retirement, compared to just 7% of Brits.
Christine Foyster, head of wealth management at HSBC, said: "People want to slow down in later life and, while some welcome the chance to stay economically active, many may not. Whereas some people regard a comfortable retirement as a natural entitlement, for a growing number this is not the case.
"Today's workers should prepare for retirement as early as possible to have some certainty for retirement. Life is full of reasons to prioritise short term spending over longer term planning, but the sooner people start saving, the less likely they will have to rely on working in old age."
Tom McPhail, head of pensions research at Hargreaves Lansdown, said: "Auto-enrolment is just the start of the solution to the pensions crisis. It is vital that everyone takes personal responsibility for the retirement savings. The three most important points to address are: am I saving enough?; is my money invested well?; and how will I draw my retirement income?
"Unless all scheme members are actively encouraged to address these questions and to plan for their retirement, it is likely that dire predictions about millions of people never being able to afford to retire are likely to come true."