A quarter of workers in the UK could be working as much as an extra 34 days each year according to the results of research by independent jobs board CV-Library.
According to its research, more than a third (37%) of UK workers put in an additional 13 working days a year, with two-thirds (64%) saying that they "often" work more than their contracted hours.
Well over half (58%) of respondents believe that the traditional nine-to-five day is an outdated concept, with almost as many (49%) attributing its demise to mobile working and the "always on" culture.
CV Library found that just a third (36%) of UK professionals still work a traditional nine-to-five day, with a worrying one in 10 working seven days a week.
Although an overwhelming proportion of respondents (86%) think that every business should offer flexible working, many of those (73%) claimed that they themselves do not have the option to work from home.
The survey revealed that three-quarters of UK professionals think that they would benefit from a four-day working week, with 40% claiming it would make staff more productive.
A quarter believe that a shorter working week would give them more time to enjoy their private life.
However, the prospect of cutting the working week did not meet with the approval of one in four, with a significant proportion of those (39%) fearing that having to squeeze their workload into less time would be stressful.
"Putting in the odd bit of overtime every now and then may be necessary," Lee Biggins of CV Library agreed, "but as a general rule you should be able to leave your work behind you at the end of the day and take time out to re-charge."