The European Court of Justice  has ruled that the UK Government must put actions in place to clean up its air quality, which could mean more restrictions for diesel and heavy goods vehicles in city centres.

The Government has already admitted that London, Leeds and Birmingham will not meet legal limits for nitrogen oxide gas (NOx) until after 2030.

The ECJ has now ruled that the UK must meet targets “as soon as possible” to force Government to put measure in place to meet an as yet undetermined shorter deadline.

The case was brought by ClientEarth, a group of activist lawyers campaigner for cleaner air, and the ECJ is expected to rule on a deadline for the UK next year.

ClientEarth blames diesel vehicles for the high levels of NOx and has said a new deadline could lead to policies such as London mayor Boris Johnson’s proposals for an Ultra Low Emission Zone in the capital from 2020 being rolled out nationally.

Alan Andrews, ClientEarth lawyer, who claims that diesel vehicle fumes are the main source of nitrogen dioxide, said: “This will force the Government to finally take this issue seriously and come up with an urgent plan to rid our towns and cities of cancer-causing diesel fumes.”

ClientEarth has also called for changes to the carbon dioxide-based motoring tax system – company car tax, capital allowances and Vehicle Excise Duty – that favours diesel vehicles over petrol-engine equivalents.

ClientEarth’s legal case refers to 16 zones in the UK where NOx limits are being breached, including Greater London, Greater Manchester, West Midlands and Glasgow.

Meanwhile, France’s prime minister Manuel Valls admitted in a recent speech that favouring diesel in the country was a mistake.

“We will progressively undo that, intelligently and pragmatically,” he said.

France has a bias for diesel sales, with the fuel choice dominating 65% of new cars sold in the first half of this year. The UK has a slight bias towards petrol with 49.8% being oil burners, while the fleet industry also has a large diesel bias due to the way taxation is based around CO2.

Part of Valls’ plans include banning diesel cars from the centre of Paris entirely by 2020. Paris mayor Anne Hidalgo told France’s Journal du Dimanche newspaper she wanted only ultra low-emission vehicles allowed in the capital. UK health campaigners have jumped on the comments from Paris calling for London to follow suit and ban diesel cars from entering the capital entirely.