Toxic air in the UK is now a “national health emergency” responsible for 40,000 early deaths and £20bn in economic costs each year, MPs have warned.

The Government’s approach to reducing air pollution amounts to little more than “box-ticking” because ministers have failed to show the “national leadership” required, a highly damning joint report by four parliamentary committees found.

The unprecedented inquiry involving almost 40 MPs said it was “unacceptable” that successive governments have “failed to protect the public” from the health risks associated with air pollution.

They said: “Air pollution is a national health emergency, resulting in tens of thousands of early deaths and costing billions of pounds in health impacts each year.

“It is unacceptable that successive governments have failed to protect the public from poisonous air. A step change in Government policy is now needed to address this.”

The joint report was compiled by four select committees: Environment Food and Rural Affairs, Environmental Audit, Health and Social Care, and Transport.

They called on the Government to introduce a range of measures to urgently get a grip on the problem.

It said a Clean Air Act should be tabled to toughen existing legislation and make clean air a legal right.

The report also called for vehicle manufacturers to be made to contribute to a ‘clean air fund’ and criticised plans to ban the sale of conventional petrol and diesel cars by 2040 as “lacking sufficient ambition”. The deadline should be brought forward to match other countries’ “more ambitious” targets, MPs said.

Paris has said it will ban both petrol and diesel cars by 2030, while Rome has outlined plans to stop diesel cars from entering the city centre by 2024.

In the UK, only 5.6 per cent of current new cars are low-pollution “alternatively fuelled vehicles”.

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The Government’s plan for improving air quality has been the subject of several successful legal challenges by environmental campaigners who argued it did not go far enough.

In their report, the MPs said: “We do not believe the latest air quality plan will deliver improvements at a pace and scale proportionate to the size of the challenge. The High Court agrees. Significant improvements to the plan, and to the Government’s wider approach to air quality, are needed to protect the public from toxic air.”

Suggesting ministers have been guilty of placing political considerations ahead of genuine action to improve air quality, they called on the Government to “place the protection of public health and the environment, rather than technical compliance or political convenience, at the centre of air quality policy”.

More support, including financial resources, needs to be given to the 45 local councils in areas where pollution levels breach legal limits, they said.

Neil Parish MP, Chair of the Environment, Food and Rural Affairs Committee, said: “The Government’s latest plan does not present an effective response to the scale of the air quality catastrophe in the UK. We are concerned that the Government is treating air quality as a box-ticking exercise. Real change will require bold, meaningful action.”

Mary Creagh MP, Chair of the Environmental Audit Committee, said: “Ministers have failed to address the polluted air in our choking cities. We need a new Clean Air Act to ensure the Government remains accountable for failures to achieve air quality commitments after the UK leaves the EU.

“The Government must ensure that after Brexit our air quality standards are as good as or better than the level we enjoy as a result of our membership of the EU.”

A government spokesperson said: "By ending the sale of conventional new diesel and petrol cars and vans from 2040, the UK is going further than almost every other European nation.

"Air pollution has improved significantly since 2010, but we recognise there is more to do which is why we have a £3.5bn plan to reduce harmful emissions. We will set out further actions through a comprehensive clean air strategy later this year.