The union says it fears a sale of the company, which is currently in protective administration.
The parent company, Delighted 2B, successfully petitioned the Belgian commercial court in the summer for protection from its creditors.
The manufacturer, which also includes the avant garde fittings maker Dark, has had a six-month period in which to turn the company around and avoid bankruptcy, but this expires in December.
Distributors have complained of extensive delivery problems with Wever and Ducre luminaires.
The Delighted 2B group operates in some 60 countries but is believed to have run into difficulties in some markets, especially Spain and Italy.