London’s mayor Sadiq Khan “lacks the legal power” to extend the ultra-low emission zone (Ulez) to the whole of the capital, five Conservative-led councils have argued in the high court. Lawyers for four outer London boroughs – Bexley, Bromley, Harrow and Hillingdon – and Surrey county council said that “key information was not disclosed” in consultations over the proposed expansion of the Ulez. The Ulez is due to expand at the end of August from the boundary of the north and south circular roads to throughout Greater London, requiring drivers of the most polluting vehicles to pay a fee when using them in the area. Most drivers of vehicles that do not meet Ulez standards – typically the oldest petrol cars from before 2006 and dirtier diesels registered before 2015 – will be liable to pay a £12.50 daily fee after 29 August. Councils launched legal action in February, arguing that Khan, was not acting in accordance with relevant “statutory requirements”, although a judge dismissed parts of the challenge in April before allowing it to proceed to the high court. The councils are seeking to block the expansion on two grounds – the legal basis for the scheme, and the consultation over the shape of a £110m scrappage scheme designed to help drivers change to newer cars or public transport. On the opening day of the two-day court hearing, Craig Howell Williams KC, for the councils, said the mayor was creating a “master charging scheme” for London, beyond his powers. He said the approach of Khan and Transport for London (TfL) would “bypass” legal “safeguards” that were “designed to ensure that any new ‘charging scheme’ is properly considered before coming into effect”. Ben Jaffey KC, representing the mayor and TfL, an interested party in the case, said in written arguments that the “primary objective” of the expansion was “to improve London’s air quality, in particular reducing nitrogen oxides (NOx) and particulates”. The barrister said Khan’s decisions would “help to get London’s air quality closer to legal limits, where they are exceeded, and World Health Organization guideline levels everywhere”. He said that the mayor had used his powers to order changes to air quality rules in London on many occasions over the last 16 years and it would be “bizarre if orders could not be amended to improve emissions standards as required”, adding that “one might expect it to have come up before now”. A verdict is not expected to be delivered by Mr Justice Swift until a later date, probably in several weeks. The Ulez, originally drawn up during Boris Johnson’s tenure as mayor, launched in central London in April 2019 and was expanded to draw about 4 million people into the zone in October 2021. Only about 6% of vehicles now entering the zone are non-compliant and pay a fee. Transport for London estimated earlier this year that about 15% of vehicles driven in outer London were non-compliant. The policy has become much more divisive in its latest expansion. TfL argues that most Londoners do not drive and poorer communities are more likely to suffer from toxic air. However, motoring organisations argue that the charges threaten the wellbeing of those who rely on their cars. Ian Edwards, the leader of Hillingdon council, said: “We believe we can win this. Quite simply, with the harm our local economies face from the effects of the proposed expansion, we can’t afford not to fight.” Campaigners said the councils were “fighting completely the wrong battle”. Areeba Hamid, a joint executive director at Greenpeace UK, said: “Every borough in the city exceeds pollution levels deemed safe by the World Health Organization … and the Ulez is one proven method to help urgently reduce the number of cars on the road, making our cities cleaner and safer for everyone.”