ClientEarth has confirmed that a “domino effect” is underway after news that Germany will put a diesel ban in place by 2019.

Aachen’s regional court ruled that the authorities must put a diesel ban in place by January 2019, to bring illegal levels of pollution in the city down. This is the result of legal action by Deutsche Umwelthilfe (DUH) and environmental lawyers ClientEarth.

The hearing was the first since Germany’s “landmark Leipzig” decision, which clarified that diesel bans can be implemented where air pollution exceeds legal limits.

According to ClientEarth, environmental lawyers say it has set the direction for all German clean air cases still waiting to be heard – and the deadline may be a blueprint for other courts.

ClientEarth’s chief executive James Thornton said: “The domino effect we expected to see is now underway in earnest. February’s ruling in the Federal Administrative Court was made it absolutely clear – diesel restrictions are not only possible, but necessary, to bring illegal and harmful air pollution down in Germany’s towns and cities. We are anticipating similar outcomes across Germany in the coming months, as our other cases are heard.

“The German government must now be proactive. It is still fighting to protect diesel when evidence suggests even the newest models can be a health threat. The diesel debacle has gone on for far too long – we need a standardised national approach and leadership from the top.”

DUH’s chief executive Jürgen Resch said: “We call on all regional governments currently struggling with illegally dirty air to put in equivalent diesel restrictions. Otherwise we will legally enforce these standards, town by town.

“The regional court has confirmed that these measures are both and proportionate and beneficial for the quality of life in Aachen, which its leadership has previously refused to accept.”

DUH and ClientEarth have brought 28 legal actions over dirty air in cities across Germany. Further cases will be heard over the next months.