Research of 2,000 employees found 87% work an average of five and a half hours more every month outside their contracted agreement which they aren’t paid for. This amounts to 153 million cumulative hours of work each month which goes unpaid – or 19 million eight-hour working days.

More than a quarter (26%) end up working more because they haven’t completed their to-do list for the day, and 20% have ‘unrealistic’ workloads for their contracted hours. As a result, 29% want their manager to take some of their work off them, while 27% want it to be more evenly distributed between the team.

Simon Garrity, UK country manager for ProTime, which commissioned the research and has compiled it into a report, ‘The True cost of Overtime: How overwork impacts employee performance’, said: “Using our time effectively is so important, especially in today’s fast-paced work environment.

“It’s concerning to see such a high percentage of adults working unpaid overtime, often due to unrealistic workloads or uncompleted tasks. Employers should prioritise workload management and ensure that employees’ time is valued and respected.”

The study also found only 6% of workers claim they aren’t very productive during their working day, while 3% admitted they are bad at managing their time effectively.

Distraction (56%), lack of focus (48%) and spending too much time on unimportant tasks (46%) were the main causes of flawed time management.

Although 71% who are good at managing their time effectively are more organised (66%), can prioritise well (57%) and make their own to-do lists (40%).

It also emerged the average worker didn’t use all their holiday entitlement for the last full working year, with 25% claiming they were unable to take the time off due to the amount of work they had to do.

For 35%, this had a negative impact on their wellbeing, with 53% suffering with increased stress and anxiety and 41% feeling tired and burnt out. Despite this, 69% of workers are generally happy with their work-life balance.

However, of those who weren’t happy, 20% are planning to leave their current job in the next six month as a result. While 14% are only staying in their job because their workload means they don’t have time to look for another one.

A poor balance also means 40% are less likely to go for a promotion and 47% are less inclined to take on additional responsibilities. The research, carried out via OnePoll, also found 42% have given up their hobbies due to work taking over, and 36% have missed important events like birthdays or a child’s nativity play.

Simon Garrity added: “The UK’s widespread culture of overwork is a ticking time bomb that is a bad deal for both bosses and workers. Excessive workloads and unrealistic expectations are burning employees out, killing motivation and productivity, and driving away top talent from organisations.

“Workers then get stuck in negative cycle, as a lack of support from managers causes overwork, which in turn harms their well-being, willingness to stay on in the job and how effectively they do their work.

“It’s important for bosses to understand unpaid work and missed holidays aren’t a sign of dedication, they are symptoms of a system which has to work better.

“Companies need to find ways to give their people fair amounts of work and make sure they have time for their families and hobbies. This will help everyone feel happier and work better.”

Dr Mansoor Soomro, Future of Work Lead at Teesside University International Business School, added: “Unrealistic workloads and overtime culture is a productivity killer. There is a clear negative and diminishing impact on productivity after a certain number of hours.

“Beyond that, mental fatigue sets in, leading to errors, decreased focus, and slower work. Exhausted employees become less efficient, negating the gains from extra hours. Secondly, overtime reduces innovation. Creativity thrives in a well-rested and balanced mind. Overworked employees have less mental energy for brainstorming new ideas or problem-solving creatively. This stifles innovation and the company’s ability to adapt and grow.”