According to the most recent data, two million people in London are living with illegal levels of air pollution. Nitrogen dioxide is one of the main pollutants and road transport is estimated to be responsible for 50% of total emissions. The consequences of high nitrogen dioxide levels are frightening and air pollution in London has caused an estimated 9,400 deaths per year. However there is some good news: nitrogen dioxide levels do now appear to be falling and could reach legal limits within 6 years. This is thanks to new policies being introduced to tackle this public health emergency, the most prominent of which being London’s world leading Ultra Low Emission Zone (ULEZ) which came into effect in central London on 8 April 2019.

In our KN Green week blog, Can law save the world?, we considered the power of judicial review as a weapon in the fight to save the environment. In particular, we highlighted the effectiveness of the three judicial reviews brought by ClientEarth over 8 years challenging the government’s failure to comply with its obligations under Directive 2008/50/EC (the Air Quality Directive). We consider in more detail here the success of these judicial reviews in holding the UK government to account over its record on air pollution and hastening the arrival of the ULEZ in London.


The Air Quality Directive was an EU Directive which came into force on 11 June 2008. It set legally binding limits and target values for concentrations of major air pollutants.

Article 13 required Member States not to exceed limit values of nitrogen dioxide set for 1 January 2010.

Article 22 made provisions for Member States to postpone deadlines for conformity with nitrogen dioxide levels by a maximum of 5 years on the condition that an air quality plan (AQP) is established in accordance with Article 23.

Article 23 provided for air quality plans to set out appropriate measures to ensure any periods in which limits for pollutants are exceeded are kept as short as possible.


By 2010, the UK Government had not complied with these requirements. In response to a letter before action from ClientEarth, the Government indicated in December 2010 that AQPs were being drawn up for Greater London and other non-compliant zones and that these plans would demonstrate how compliance would be achieved by 2015. When draft AQPs were published on 9 June 2011, they showed that in 17 zones, including Greater London, compliance was expected to be achieved after 2015.

The first judicial review was issued on 28 July 2011 seeking declarations that the draft AQPs did not comply with the requirements of EU law and that the UK was in breach of its obligations under Article 13 of the Air Quality Directive. The Government argued that it was under no obligation, under Article 22(1), to put a plan for reducing nitrogen dioxide levels below limit values to the Commission by 1 January 2015.

When he heard the claim on 13 December 2011 ([2011] EWHC 3623 (Admin)), Mr Justice Mitting agreed with the Government and refused to make any mandatory orders or declarations, finding that Article 22(1) was discretionary. He observed:

It is clear from all I have seen that any practical requirement on the United Kingdom to achieve limit values in its major agglomerations, in particular in London, would impose upon taxpayers and individuals a heavy burden of expenditure which would require difficult political choices to be made. It would be likely to have a significant economic impact.” - Para. 15 [2011] EWHC 3623 (Admin)

Mr Justice Mitting agreed that the Government was in breach of its Article 13 obligations but did not agree that it was necessary for him to declare that this was so.

ClientEarth appealed unsuccessfully to the Court of Appeal where Laws LJ agreed with Mr Justice Mitting that Article 22 was discretionary ([2012] EWCA Civ 897). The Supreme Court heard the appeal on 7 March 2013 and granted the declaration that the UK government was in breach of Article 13. The Court made a reference to the CJEU seeking answers to questions of:

  1. whether or not a Member State is obliged to seek a postponement of the deadline in accordance with Article 22;
  2. if so, can a Member State be relieved of that obligation?
  3. If not, and no application under Article 22 is made, does Article 23 apply?
  4. What remedies must the national court provide? (Para. 39 [2013] UKSC 25)   

The UK’s submissions to the CJEU in these proceedings made mention for the first time to what they called a “game changing” proposal by the Major of London for the ULEZ in central London from 2020.

In a judgment dated 14 November 2014 (Case C-404/13) the CJEU replied that:

  1. Article 22(1) does require a member state to apply for a postponement and establish an AQP where it cannot comply with limits for nitrogen dioxide levels.
  2. Where a member state has not complied with Article 13 or applied for a postponement under Article 22(1) it is for the national court to take necessary measures to ensure the national authority establishes an AQP.  

With this judgment, it was back to the Supreme Court ([2015] UKSC 28) where the Court noted developments which had occurred since the claim had last been before them. In February 2014, the European Commission had launched formal infringement proceedings against the UK for failure to meet the nitrogen dioxide limit values. The CJEU made clear in their ruling that this enforcement action did not detract from the responsibility of the domestic courts for enforcement of the Directive. In light of this, it was “untenable” for the Supreme Court to agree with the High Court and Court of Appeal that compliance was a matter for the Commission.

The Supreme Court accordingly issued “a mandatory order requiring the Secretary of State to prepare new air quality plans under article 23(1), in accordance with a defined timetable, to end with delivery of the revised plans to the Commission not later than 31 December 2015”. - Para 35 [2015] UKSC 28


Following the decision of the Supreme Court, on 17 December 2015 Defra published the Government’s 2015 AQP which addressed the need to reduce nitrogen dioxide emissions. ClientEarth sought a declaration that the 2015 AQP, like its predecessor, failed to comply with Article 23(1) of the Directive and sought an order quashing the AQP. Defra opposed the claim and the Mayor of London joined as an interested party in support of ClientEarth. This second judicial review was heard on 18 and 19 October 2016 [2016] EWHC 2740 (Admin).

ClientEarth argued that the AQP was unlawful for two reasons:

  1. The Government was not complying with the requirements of Article 23 to achieve compliance in as short a time as possible.
  2. The Government was putting considerations of cost, political sensitivity and administrative difficulties ahead of the Directive’s primary purpose of protecting human health.

The Mayor of London argued that he needed to be granted additional powers and funding from central government.

This second time round, ClientEarth had a lot more success in the Administrative Court. In his judgment, Mr Justice Garnham rejected the government’s arguments that cost could justify an extension of the target date for compliance and criticised the government for its failure to ensure compliance as soon as possible. The 2015 AQP was quashed and the Government ordered to draft a new one. There was no appeal by Defra.


On 26 July 2017 Defra published the third AQP in purported compliance with Mr Justice Garnham’s order. This AQP was also challenged by ClientEarth via a judicial review and again they were successful [2018] EWHC 315 (Admin).

The challenge this time was on the grounds that a substantial number of local authorities were unaccounted for. Mr Justice Garnham agreed with ClientEarth that the government was failing in its obligations by simply asking local authorities to take action rather than requiring them to comply. Justice Garnham concluded (Para 108 [2018] EWHC 315 (Admin)) with an unequivocal assessment of the government’s failures on air pollution since 2010:

It is now eight years since compliance with the 2008 Directive should have been achieved. This is the third, unsuccessful, attempt the Government has made at devising an AQP which complies with the Directive and the domestic Regulations. Each successful challenge has been mounted by a small charity, for which the costs of such litigation constitute a significant challenge. In the meanwhile, UK citizens have been exposed to significant health risks.”

The power of judicial review

Although the UK Government is yet to comply with the Air Quality Directive, they have taken steps to achieve compliance sooner than their previous plans allowed for and the introduction of the ULEZ zone in London a year earlier than originally planned is just one example of the acceleration of attempts to achieve compliance in light of the rulings of the courts.

It is not just Londoners who have benefited from the ClientEarth successes. As a result of the February 2018 ruling, the UK Government was forced to create a supplement to their 2017 Plan legally directing 33 local authorities outside London to conduct feasibility studies to bring forward compliance with nitrogen dioxide limits by 2021.

Without ClientEarth’s persistence over 8 years, it is hard to imagine that the UK Government would have put these measures in place or at least put them in place by now. Not only did ClientEarth have to issue 3 expensive judicial reviews, but there also had to be an intervention from the CJEU to get the domestic courts to agree to hold the UK Government to account. The domestic courts initially agreed with the Government’s arguments that the expense and difficulty of putting measures like the ULEZ in place were relevant factors in justifying their failure to take the Air Quality Directive seriously enough.

When (or if) we leave the EU, we will have to hope that in any future environmental challenges the English courts will properly challenge and scrutinise the Government’s compliance with its environmental obligations.