The European Commission urged Germany to take urgent steps to regulate polymer producers under the bloc's Emissions Trading System (ETS) or face being sued over the breach of EU law.
The EU executive sent Germany a formal request to comply after Berlin failed to give a satisfactory response to an initial plea to include the sector in the ETS, which regulates around half of Europe's greenhouse gas output.
"We are asking Germany to include polymers in the EU ETS as all countries do," a Commission spokesman said in an emailed response to questions following the publication of a monthly statement listing infringements of EU law.
The bloc's flagship policy to tackle climate change, the EU ETS forces over 13,000 power plants, factories and airlines to surrender an EU Allowance for every tonne of carbon dioxide (CO2) they emit.
Under new rules, last year governments were required to expanded coverage by around 6 percent EU-wide to include new sectors including polymer and other chemical producers.
Under new rules, last year governments were required to expanded coverage by around 6 percent EU-wide to include new sectors including polymer and other bulk chemicals produced by firms including BASF, Dow Chemical and Solvay .
Officials at Germany's emissions trading authority were not immediately available for comment.
The Commission also said it will ask the European Court of Justice to consider whether to sue Poland over its failure to declare what penalties it will impose on firms for breaching EU laws regulating fluorinated gases.
These so-called "super" greenhouse gases are used in fridges and air conditioners and have a global warming potential thousands of times greater than CO2 but are regulated separately from the ETS.
In the same statement, the Commission said it has also urged Poland to fully implement EU laws designed to enable CO2 emissions to be safely captured and buried underground and to reduce the CO2-intensity of transport fuels.