The study, by workplace pensions business Punter Southall Aspire, also showed that of those who have not retired yet, 43 per cent plan to retire before they turn 65 and another 17 per cent plan to retire fully before the age of 70.
Of those who have already retired, two-thirds have stopped work completely.
Peter Selby, managing director, Retail Advice, at Punter Southall Aspire, says the figures have revealed “a growing trend” for people to continue working into retirement, whether through necessity or boredom.
He said: “Once upon a time, you hit ‘retirement age’ and that was it, you stopped work.
“Some people even retired early in their 50s.
“Most expected to enjoy a few golden years in retirement and be able to fund that time.
“However, our survey reveals a changing picture of retirement that mirrors the broader UK outlook and underlines the growing need for people to save for their retirement.”
The Office for National Statistics (ONS) projected that more than a quarter of UK residents will be aged 65 years or over within the next 50 years.
ONS figures for December 2017 to February 2018 highlighted that just under 1.2 million people over the age of 65 were in work - or 10.2% of the entire age group.
Mr Selby added: “Many people hitting retirement today, who may be living well into their 80s and 90s, won’t necessarily have sufficient money to stop work at 65, so more and more are working way beyond state pension age.
“Our survey suggests even if people have built up an adequate pension pot, they don’t necessarily want to stop work.
“Some people feel at the peak of their career at 65, and still have a lot to contribute. They are still healthy, so even if they want to slow down, they might still have plenty of energy and find retirement a drag.
“We advise people to take note of these trends to assess their own situation, whether they are nearing retirement or a few decades off.
“What people do today with regards to pension saving can have a big impact on whether they have the choice to retire or not.”