The European Union began legal action on Thursday against Germany, the United Kingdom and five other member states for failing to police emissions test cheating by carmakers after the Volkswagen diesel scandal.

Amid mounting frustration in Brussels over what EU officials see as governments colluding with the powerful car industry, the European Commission is wielding its biggest available stick in an attempt to force nations to clamp down on diesel cars spewing health-harming nitrogen oxide pollution.

German officials - who say the EU law is poorly framed - had expected Brussels to stop short of confronting the EU's leading power and by far its biggest car manufacturer.