An increase in the minimum holiday entitlement from today means a fifth of employees (21%) are in danger of not getting the holidays they are entitled to if their holiday allowance stays the same.

A survey from YouGov and Croner shows a quarter of 2,114 adults surveyed claim they are entitled to fewer than 27 days off a year, including bank holidays, and 6% of employees are entitled to fewer than 24 days.

From today (1 April) employers will be legally obliged to give all staff at least 28 days off work, meaning 16% of employers of full-time workers will be in breach of the law unless they increase holiday entitlement.

Gillian Dowling, employment technical consultant at Croner, said: "Money and holidays are often the key motivators when searching for a job and are an essential part of an employment contract. At the moment it seems not everyone is aware of their rights.

"The real danger for employers is when their staff become more switched on. If they have not asked already for extra holiday, they will do soon."