A robust plan to clean up illegal levels of air pollution, which could have a major impact on fleets, will have to be drawn-up by the new Government following the General Election.

Client Earth, a group of activist lawyers which also runs the Healthy Air Campaign, brought a case against the Government after it failed to meet legal limits for air pollution.

After a five-year battle in the UK and European Courts, the case is now nearing its conclusion following a Supreme Court hearing.

A judgement is expected within the next three months and will be binding on the Secretary of State for the Environment, Food and Rural Affairs, irrespective of who forms the new Government.

The hearing followed last year’s ruling from the European Court of Justice (ECJ), which said the UK must have a plan to achieve air quality standards in the ‘shortest time possible’.

Client Earth lawyer Alan Andrews said: “The Supreme Court heard that Government plans won’t achieve compliance with legal limits until after 2030. How soon after 2030, isn’t clear. We are hopeful that after our five-year legal fight, the judges will uphold the right to breathe clean air.”

Client Earth claims that diesel is the biggest culprit in the fight to improve air quality and reduce vehicle pollution. Potential measures to reverse the ‘dieselisation’ of the UK car parc could include: changes to company car benefit-in-kind tax and other carbon dioxide-based motoring taxes, including: Vehicle Excise Duty and capital allowances; and a national roll out of ultra low emission zones, replicating London Mayor Boris Johnson’s proposals for the capital from 2020.

Client Earth’s legal case refers to 16 zones in the UK where nitrogen dioxide limits are being breached. They include: the West Midlands; Greater Manchester; West Yorkshire; Teesside; Southampton; Glasgow; and Greater London.

The ECJ said that the Government’s existing proposals for cutting pollution would not meet nitrogen oxide limits until after 2030 - 20 years after the original deadline.

Supreme Court judges are now considering the ECJ ruling and will decide whether or not the Department for Environment, Food and Rural Affairs (DEFRA) should be forced to produce a new air quality plan and, if so, with what stipulations, to tackle nitrogen dioxide pollution targets in a much shorter timeframe. Any future plan is likely to mean a focus on diesel vehicles.

The ‘dieselisation’ of the UK car parc - to which massive growth in corporate use of diesel engined company cars and vans has contributed - is being blamed for air quality below European standards.

The Government’s lawyers told the Supreme Court that DEFRA was currently revising its air quality plan which would be “extensive” and cover national and local measures.

However, the Supreme Court was also told that producing an air quality plan was a complex process and it was not possible to produce a quick plan due to the General Election and the requirement for public consultations. The Government is expected to take its plan to the European Commission by the end of 2015.

It said it is “committed to improving air quality” and added it “recognises that clear air is vital for people’s health”. It promised to “continue to work” to ensure that air quality ceilings were “set at the right level of ambition based on evidence”.

Responding last month (March) to the House of Commons’ Environmental Audit Committee report ‘Action on Air Quality’, the Government said it was currently carrying out a review to update its air quality plans. It added: “The use of both individual low emission zones and a national approach will form part of the review.”

The Government said its goal was to “support measures to encourage cleaner, more sustainable vehicles and transport systems. We have taken a fuel neutral approach to achieving this objective”.

Ruling out any introduction of subsidising a diesel scrappage scheme or engine emission control retrofits, the Government said: “As part of revising our national air quality plans by the end of 2015, all feasible measures are being investigated further to ensure an effective package of measures is developed to deliver compliance in the shortest possible time.”