Employers are being urged to ensure that staff take their full holiday entitlement.
The call came as a study showed that two out of five managers did not take their full entitlement of annual leave last year.
A third of those who missed out on holidays could not carry forward days owing, with some losing a full week.
The results come from research among 1,000 managers by the Institute of Leadership and Management reported in The Times.
The institute said 40% of managers agreed that there was room for improvement in their work-life balance.
Chief executive Chris Elvin said: “Workers come back from leave refreshed, relaxed and revitalized, which is ultimately great for business.
“It should be a top priority for employers to make sure their employees use it rather than lose it.”