The European Commission formally took Germany to task for breaching rules on the environment Thursday in a row over automaker Daimler's air conditioning coolant.
In a letter of formal notice, the first step in an infringement procedure, the Commission demanded Germany "fully apply" rules after vehicles "not in conformity with EU law were placed on the EU market by a German manufacturer".
Since last year, EU norms demand that car makers use a refrigerant called R1234yf.
But Daimler is sticking to an older coolant, called R134a, as it claims studies show the new one catches fire more easily and puts cars at a greater risk of explosion in case of a crash.
The makers of R1234yf, US chemicals giants Dupont and Honeywell, reject Daimler's claims.
In Germany, the auto giant was given special permission to keep using the older coolant, despite initial approval of the new one by the German Automakers Association, VDA, of which Daimler is a member.
Germany has two months to respond to the letter or it will face court action.
Explore further: EU raps Daimler over new coolant rules