Germany's VDIK foreign carmaker association opposes new rules that will require dealers to disclose new cars' energy efficiency.
The German ministries for the economy and environment have agreed on future labeling rules that will require new cars in dealer showrooms to display a color-coded energy efficiency scale based on CO2 emissions and vehicle weight.
The VDIK says the efficiency classes only make sense if there is uniform labeling for all of Europe.
It is illogical for a model to be classified differently in different countries, said VDIK President Volker Lange.
"This approach is not reasonable for the consumer or for dealerships," he said.
ZDK, the German Association for Motor Trade and Repairs, opposes the way the labels will be determined.
It wants the labeling to relate to the type of vehicle, and not to the figures themselves. Otherwise, the scheme would compare "apples and oranges," the ZDK says.
All vehicles with the appropriate advanced technology must have the opportunity to be classified in the favorable energy efficiency categories, it said.
Germany's Economy Minister Rainer Bruederle said German automakers are supporting the new regulations.
The labeling establishes "persuasive incentives for the improvements in energy efficiency in all vehicle segments" and offers consumers "valuable assistance in their decision-making," he said in a statement.