One in five workers does not take all their holidays and many of those who do go away end up keeping in touch with the office, according to new research.
A survey of 2,000 adults by financial firm LV= found that a fifth wasted a week's holiday every year, giving their employer hundreds of pounds worth of free work.
Heavy workloads and worries about job security were among the reasons given for not using up holiday entitlements.
One in four of those surveyed said they worked while on holiday.
The report said people needed three and a half days off before they felt properly relaxed.
Selwyn Fernandes, managing director of LV= travel insurance, said: "In these uncertain economic times many people find themselves not only with less money, but also with heavier workloads.
"Yet a few days off is good for our general wellbeing. With people continuing to worry about work while they are away it is important to have adequate travel insurance to take away any other holiday worries."