Business managers in the UK work on average an extra day each week through unpaid overtime, according to new figures from the Institute of Leadership in Management (ILM).

The pressure of heavy workloads and mobile access to email messages through smartphones means many bosses work additional hours when they should be resting, it said.

According to its figures around one in eight managers work an extra two days per week, such are the demands of their job.

"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.

He added: "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."

The ILM figures show around two-thirds of managers feel under pressure to work extra hours by their bosses.