Managers 'work extra day per week in unpaid overtime'
Almost half of UK managers work an extra day of unpaid overtime per week, a study into working practices has suggested.
Work pressures and easy access to email through smartphone technology leave over 90% of managers working outside contracted hours, the study found.
Around 13% of managers work two days unpaid overtime per week, the Institute of Leadership and Management said.
Business lobby group CBI said UK firms are addressing the issue.
Around two thirds of UK managers feel under pressure to work extra hours from their employers, the Institute of Leadership and Management (ILM) said.
"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 ILM chief executive Charles Elvin.
"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.
An online survey of 1,056 ILM members found that 76% routinely work late in the office or at home, 48% regularly work through their lunch-break, and more than one third work at weekends.
Smartphone technology has added to pressures to work, with some managers "obsessively" checking email outside of office hours, Mr Elvin said.
"We all know how stressful it can be to receive an urgent late night email when you feel compelled to respond immediately," he said.
Research body the Work Foundation said that overwork can lead to underperformance.
"When you work excessive hours this can lead to employee burnout, increased stress, depression and physical illnesses," said Zofia Bajorek from the Work Foundation.
However, if smartphones are used to allow flexible working hours, this can support the organisation, the employee and the customer, she added.
The employers' organisation the CBI said that businesses investing in employee wellbeing "is not only the right thing to do, but it also has real business benefits."
"Having healthy staff is an essential part of running a healthy business," said Neil Carberry, CBI director for employment and skills.
"Businesses are looking at how they can work with employees to manage workload and we're already seeing many firms focusing on health management and building employee resilience to help keep their staff happy and healthy."