The Greek government has defended its new six-day working week policy, saying it is an "exceptional measure" that would only be applied in "specific circumstances."

Greece introduced in early July new regulation that gives employees in some businesses the option of working an extra two hours each day, or adding another eight-hour shift to their schedule — meaning they could work 48 instead of the traditional 40 hours a week. The policy does not cover the food services and tourism businesses.

Outrage about the policy spread on social media as the regulation was met with backlash from labor unions and political observers criticizing the move. When the policy package containing the bill was first announced last September, thousands protested against the new policies.

Some critics have raised concerns about whether the policy could be extended to other sectors and businesses or mean employees would not be compensated fairly or be overworked.

"It is important to note that this new regulation does not in any way affect the established 5-day/40-hour working week mandated by Greek law, nor does it establish a new 6-day working week," Greek Minister of Labour and Social Security Niki Kerameus told CNBC in emailed comments late last week.

"All it does is provide only in limited circumstances for the option of an additional working day, as an exceptional measure."

Only two types of businesses fall under the regulation — namely those that operate 24 hours of the day, seven days a week with rotating shifts, and those that operate 24 hours a day for five or six days of the week, also using rotating shifts, Kerameus said.

Especially for businesses that are not operational every day, "the additional working day option is permissible only in the case of an increased workload," Kerameus explained.

The minister said new regulations would protect employees from their work not being officially declared in the right way, which means they can now be compensated fairly. For example, workers could see their salaries rise due to the increase in hours, she added.

"Additionally, the law stipulates more measures to ensure the protection of workers, such as guaranteed days off, specific working hours, and safeguards against unfair dismissal," she said.

Data from the Organization for Economic Cooperation and Development shows that on average, workers in Greece worked longer hours than those in the U.S., U.K. and across the European Union in 2022. Greek employees on average worked over 300 hours more a year than the EU-wide average.

Kerameus said many other countries have measures and stipulations in place that are similar to Greece's new policy.

"Most countries in Europe have similar provisions for exceptional additional working days. So Greece is not doing anything different," she said.