Research by the Institute of Leadership and Management has revealed that 94% of managers work over and above their contracted hours every week.
The survey of 1,000 ILM members also showed that around two thirds of UK managers feel under pressure to work extra hours.
The findings suggest that overtime is firmly embedded in UK working culture, with 76% of people routinely working late in the office or at home.
In addition, almost half of respondents regularly worked through their lunch break and more than 38% worked at the weekend.
"When you add up all the skipped lunch breaks, early morning conference calls and after hours emails you see just how widespread the extra hours culture is within UK business," said Charles Elvin, chief executive of the ILM.
"Of course, all organisations face busy periods when employees will feel motivated to work above and beyond their contractual hours. But excessive hours are not sustainable - there are only so many times you can burn the midnight oil before your performance, decision making and wellbeing begin to suffer," he added.
The research also revealed that more than half of ILM members felt they had to work extra hours to complete their workloads, with the main out-of-hours tasks being catching up on emails (78%), reading papers and documents (32%) and dealing with urgent or time sensitive matters (30%).
The findings follow a poll by Ovum Analysts for Samsung Business Futurescape, which found that up to 78% of employees use their own devices for work.
The study also revealed that some are setting up their own applications, such as cloud file sync and share services, as 18% of workers believe their employers' IT departments do not provide them with the resources they need to do their jobs.