More than four out of five professionals work more than their contracted hours - and a third never take a lunch break, according to new research.
The study suggests businesses are facing an "alarming" burnout epidemic with 81 per cent of employees working beyond their contracted hours.
And those that work in high level positions are twice as likely to work more than 10 hours over their contracted hours (42 per cent) as those at entry level (21 per cent).
The survey of 2,600 professionals in sectors such as banking and finance by global professional services recruiter Morgan McKinley found that 75 per cent of employees felt obligated to work beyond their contracted hours.
But businesses are not rewarding these staff, with only around one in eight (13 per cent) saying that they are compensated for working extra hours.
The figures revealed that less than a third of professionals (32 per cent) believe that they are productive during the extra hours that they work.
A third (34 per cent) don't take their lunch break at all, with millennials (21 per cent) being the largest group to have a working day without their lunch break.
When they do finally leave the office, three out of four are "sometimes" or "always" working from a mobile device.
Almost half of C-level professionals (46 per cent) work outside the office from their mobile - but only one in 11 entry level do so (nine per cent), according to the survey.
David Leithead, UK chief operations officer at Morgan McKinley said: "Many people work more hours than they are paid for, often because they feel obligated to, rather than because of a belief that it's a productive exercise.
"Businesses are facing an alarming burnout and need to evolve work practices.
"During the day, many employees don't take any kind of lunch break. Then three-quarters of them feel obligated to work beyond their contracted hours, yet they don't feel that is productive.
"And when they do finally leave the office, they are always on-call. If not managed carefully, these factors can cause employee stress and burnout, and poor business performance."
He said many businesses have a widening gap between modern business philosophy around "smart" working, and the reality of old-fashioned noses to the grindstone.
More than half the professionals polled said they believe more flexibility would add to their productivity, showing the demand for flexible work arrangements.
Although more employees do have the option to work from home and flexible start-finish times, the findings suggest a culture of flexible working is not yet embedded.
The majority indicated flexible and remote working arrangements are offered on a discretionary basis or in extenuating circumstances rather than as part of an overall package.
Mr Leithead added: "Employers may have good intentions but many have a long way to go in finding a solution, helping their employees to find the right balance and re-educating old school management to ensure that they attract and retain talent.
"Not least because the new millennial generation won't embrace this, they simply won't put up with it - which spells longer term problems that big companies can't afford to ignore."