But legal experts believe the ruling opens a number of grey areas for employers when deciding on policy and this increases the dangers of employees abusing the system
Owen Warnock, employment lawyer at Eversheds, said: "Many employers take the view that if an employee is sick while on holiday, that is just bad luck for them.
"What if a worker falls ill after their annual leave has started? When this happens what evidence of illness must the worker produce in order to have their leave reclassified? After all, if they were not on holiday the employer would have to accept a self-certificate for the first week of sickness.
"The danger of abuse is clear: an employee could increase his or her holiday entitlement by ensuring that in most years they alleged they were sick while on holiday. It may only be the occasional ‘bad penny' employee who does this, but the resentment that it would create with colleagues should not be underestimated.
"Until the European or UK courts say otherwise, our view is that employers are entitled to require workers to produce convincing evidence of their illness while on holiday and that it would have rendered them unfit for work before allowing workers to ‘reallocate' holidays."