Workers who fall ill during their holidays could now claim the time back from their employers following a landmark European Court of Justice judgment that lawyers warned was open to abuse.
The court ruled that employees had the right to ask for statutory leave to be "reallocated" when it was spoilt by sickness.
Under the terms of the judgement, employees would even be allowed to carry any annual leave ruined by illness over into the next holiday year.
The ruling is effectively a new interpretation of the European Working Time Directive on workers' hours, which applies in Britain across the entire private and public sector.
Leading employment lawyers warned it would be costly for businesses and that it left "the door open for abuse" by unscrupulous employees seeking to bolster their holiday entitlement by simply claiming to have a cold or flu while on leave.
A worker could phone up while on holiday and report in sick in the normal way - taking the day off sick, rather than counting it against their annual leave entitlement.