Two out of five managers returned to work after a holiday feeling more stressed than when they left, according to new research.
A survey of 2,500 managers found that one in three worked while they were on leave, often responding to emails or answering work-related phone calls.
The Institute of Leadership & Management said it was concerned with its finding that many staff returned to to the office feeling more stressed.
Chief executive Penny de Valk said: "Gone are the days when people cut off contact with work for a fortnight over the summer and made a complete break.
"While technology means that it is easier than ever to work remotely, it also makes it extremely hard to switch off.
"Uncertain economic times also mean that many UK employers are keeping one eye on their job at all times, when what they really need is time away from the office to rest and re-energise."
Most of those questioned complained that they returned from holiday to a "deluge" of emails and were anxious about the heavy workloads they faced after a break.
The institute urged employees to limit any contact with their office while they were on holiday and suggested not opening emails immediately after returning to the office.