The lawsuit seeks to set a precedent that would enable owners of Mercedes GLC and GLK vehicles to gain compensation for software that was allegedly used to trick emissions tests.
The lawsuit covers nearly 50,000 GLC and GLK models and was made possible after Germany passed a law in 2018 that allowed consumer protection organizations to litigate on behalf of the consumers they represent, avoiding the high legal costs that could discourage people from bringing legal action.
Mercedes said the claims by diesel customers as well as the lawsuit were unfounded.
Over 25,000 such claims have been brought before courts — 95 percent of which have failed, the automaker said.
The matter is part of the wider emissions scandal that has cost rival Volkswagen Group billions of euros in vehicle refits, fines and legal costs.