Britons who don't take all their holiday entitlement are effectively giving employers £1.2bn-worth of free work - more than 14 million days - according to a poll by online travel company Expedia.co.uk.
The survey of 2,000 people revealed that one in eight said they rarely had a holiday from work, while one in 10 said they put in a working week of at least 50 hours.
More than a third of those questioned said they believed workers were afraid to ask for time off, which was fuelling the UK's long-hours culture.
One in four also said they took a "sickie" when they couldn't face going in to work.
