Clientearth No.3, R (on the application of) v Secretary of State for Environment, Food and Rural Affairs & Ors

Under Article 23 of Directive 2008/50/EC, an air quality plan must be prepared for each zone where limit values are exceeded. It must aim for compliance by the soonest date possible, reduce exposure as quickly as possible, and make compliance likely. Cost cannot justify omitting or weakening measures, although it may be considered where alternative measures are equally effective. Plans must identify measures, implementation timetables, expected improvements and the time needed to achieve them. General encouragement to local authorities is insufficient where the competent authority must ensure compliance. A plan may use a benchmark measure, such as a charging clean air zone, but the benchmark cannot dilute the statutory obligations applicable to individual zones.

ClientEarth challenged the Government’s third air quality plan for nitrogen dioxide, published on 26 July 2017 after earlier plans had been quashed or found deficient. The challenge concerned the treatment of 45 English local authority areas, five English cities, and the Welsh air quality plan.

The central issues were whether the plan contained sufficient enforceable measures and information to secure compliance with statutory nitrogen dioxide limits, whether its timetables were legally adequate, and whether the Welsh plan complied with the Directive and domestic Regulations.

1. 45 English local authority areas. The Government could properly use charging clean air zones as a benchmark and there was no challenge to that approach for the 23 authorities or the five cities. It was unlawful, however, to apply the three-year charging-zone benchmark to the 45 areas as a substitute for the obligations under Article 23 of Directive 2008/50/EC. For each relevant zone, the Secretary of State had to pursue the earliest possible compliance date, the quickest route to reducing exposure, and measures making compliance likely.
2. Cost was not a lawful reason to omit or weaken measures. It could be relevant only where two measures were equally effective in achieving the objective. Letters encouraging local authorities to take action did not satisfy the duty to ensure that compliant plans were established and implemented.
3. The local plans also failed in form. Lists of completed, proposed or investigated measures did not provide the required description of measures, implementation timetables, estimates of air-quality improvement and expected attainment periods under Annex XV of the Directive and Schedule 8 of the English Regulations. The Secretary of State had to devise a mechanism, described by the judge as potentially including feasibility studies, requiring the authorities to develop appropriate plans.
4. The modelling and monitoring challenge failed. The national modelling complied with the Directive’s criteria, and no clear legal error or irrationality had been shown.
5. Five cities. The December 2017 Ministerial Directions requiring full business cases by 15 September 2018 supplied the necessary legal first step. The Directive and Regulations required a timetable, but not that every stage of the timetable be legally mandated from the outset. The approach was rational and lawful.
6. Wales and relief. The Welsh Ministers accepted that the Welsh plan was non-compliant. The court concluded that the 2017 Plan was unlawful for the 45 English areas and Wales, and indicated that it would be minded to make a declaration and mandatory order requiring an urgent supplementary plan while leaving the existing plan in force pending its production. Relief was reserved.

• Supreme Court: The first air quality plan was quashed and a mandatory order was made in [2015] UKSC 28.
• High Court (Administrative Court): The second plan was found deficient in the November 2016 judgment, cited as [2016] EWHC 2740 (Admin).
• High Court (Administrative Court): In the present proceedings, the 2017 Plan was declared unlawful in specified respects, with relief reserved.