The European Union (EU) has opened legal action against seven nations, including the UK, over their response to the Volkswagen emissions scandal.
Four – the UK, Germany, Luxembourg and Spain – have been criticised for failing to take action against Volkswagen for cheating emission tests. They were accused of not imposing similar penalties to those faced by VW in the United States over VW's use of illegal software to hide emissions on tests.
The other nations involved are Czech Republic, Greece and Lithuania – for not even including the possibility of fining car firms over potential violations.
Member states have been given two months to answer and if they fail to respond to concerns raised in Brussels, the EU could take them to court in Luxembourg.
And the European Commission's not happy with the UK and Germany specifically, saying they refused to share details on breaches of EU emissions laws found in national investigations.
In a statement, industry commissioner Elzbieta Bienkowska said: "National authorities across the EU must ensure that car manufacturers actually comply with the law."
Germany has said the current EU laws are poorly framed. Under EU law, member nations are responsible for overseeing whether cars do indeed meet standards.
Investigations across the UK, France, Italy and Germany uncovered the use of cheat devices, though no action has been taken against VW.
It has agreed to pay $15bn in a settlement with US authorities and owners of around 500,000 vehicles. Around 11m cars across the world have the software.
Last month, Sadiq Khan wrote to Volkswagen after Transport for London (TfL) found that an estimated 80,000 of the 500,000 VW cars registered to addresses in the capital were fitted with illegal defeat devices and so had escaped the congestion charge for years.
He called on the car giant to "reimburse TfL the £2.5m lost in congestion charge revenue".