Businesses could lose millions of kroner as a result of a change to holiday rules made this May.

Under the new rules, made after a precedent-setting case in the EU courts in 2009, employees that become ill during their holiday are entitled to take the days lost to illness at another point in the year.

But now the employers' association Dansk Arbejdgiverforening (DA) has warned that the rule chance could prove costly for businesses.

“We have calculated that it could cost private sector employers about 150 million kroner a year but we definitely hope that number will be lower,” Flemming Dreesen, head of employment law at DA, told Frederiksborg Amts Avis.

The new rules stipulate that if a person is sick for more than five of their 25 annual holiday days they can be compensated with extra days off.

This is to ensure that employees are given enough time off to fully recuperate, though there are fears that the new rules will be abused.

To deter fraud, employees have to prove that their holiday illness was so severe that they would have been unable to work by providing documentation from a doctor. An individual seeking such documentation would have to pay for the doctor's appointment.

Employers would be faced with an extra expense, even if the claims are legitimate, but Johnny Skovengaard, deputy chairman of the trade union 3F, argued that everyone is better off with the new rules.

“Employers see it as adding extra costs and it’s true that if you have five employees and two get sick then it will end up costing,” Hansen told Frederiksborg Amts Avis. “But we don’t expect that it will add so many more expenses for employers.”