The city of Ninove has asked shop staff not to speak French among themselves in the presence of customers, saying the measure is intended to preserve the Flemish character of the city.
The request comes from the municipal administration, where the far-right party Forza Ninove holds an absolute majority.
According to local officials, the move follows complaints from customers who said they felt excluded or confused when shop workers spoke French with each other in stores.
Some residents reported feeling like "foreigners in their own city", local councillor Evi Bické said.
City authorities held discussions with managers of several shops at the Ninia shopping centre, during which they said staff were expected to speak Dutch when customers were present.
Officials said using Dutch is important to ensure accessibility and a welcoming environment for customers. Further discussions with other shops are planned.
It remains unclear whether any sanctions will be imposed if the request is not followed.
Belgium's constitution guarantees freedom in the use of languages, except in cases specifically regulated by law.
Language use between private individuals is generally unrestricted.
