Reducing speed limits on certain motorways and removing speed humps in towns with high levels of pollution are among measures suggested by Government in its revised air quality action plan, which was published on Friday.

But it will leave it to local councils to develop their own proposals to bring pollution levels within the legal limits and has made no firm commitment to introduce a scrappage scheme for diesel vehicles.

Environmental law firm Client Earth says the plan “lacks ambition and detail” and the Mayor of London described it as a “weak plan that lacks any urgency”.

The Government’s draft plan acknowledges that diesel vehicles are the main source of nitrogen dioxide pollution alongside roads in many urban areas and lists 40 English local authorities with one or more roads that persistently exceed legal limits. It adds that it is now for local authorities “to develop local proposals likely to achieve the air quality limits within the shortest time possible”.

Emphasis is placed in the plan on the need to develop clean air zones in English towns and cities where action is needed to improve air quality. It says that local authorities introducing such zones could consider charging certain types of vehicle to enter or move within the zone, but only if they “fail to identify equally effective alternatives”.

Other measures listed which local authorities could consider include improving road layouts to optimise traffic flow, encouraging the uptake of ultra low emission vehicles – including the provision of adequate charge points – and promoting car sharing, the use of public transport, walking and cycling.

Government’s draft air quality action plan is now out for consultation and it says it will finalise its plan for tackling nitrogen dioxide pollution by the end of July. Publication of the draft plan last Friday followed a High Court ruling that it must be published by 9 May.

Client Earth chief executive James Thornton said: “The court ordered the Government to take this public health issue seriously and while the Government says that pollution is the largest environmental risk to public health, we will still be faced with illegal air quality for years to come under these proposals.”

He added: “The Government seems to be passing the buck to local authorities rather than taking responsibility for this public health emergency.”

On the issue of clean air zones James Thornton said: “We fail to see how the non charging clean air zones, proposed by the Government, will be effective if they don’t persuade motorists to stay out of those areas.”

He also expressed disappointment that Government failed to commit to a diesel scrappage scheme.

London Mayor Sadiq Khan said that Government’s proposals do not go far enough. “We've dragged the Government kicking and screaming through the courts to produce these belated proposals – but they are toothless and woefully inadequate,” he wrote.

“Whilst I'm pleased the Government has not ruled out my proposals for a targeted diesel scrappage fund there is no commitment to it.” And he added: “The Government’s proposals don’t include a commitment for a new comprehensive Clean Air Act and there’s no commitment to changes to vehicle excise duty to encourage people to buy cleaner cars.

“This is a weak plan that lacks any sense of urgency. That means thousands of people will continue to die prematurely and unnecessarily, and many more children having to live with long term health problems.”

CIHT said that on initial reading some of the interventions in the air quality plan could be of use.

It said cleaning up exhaust emissions and developing new vehicle technologies can help improve the quality of the air we breathe, but added that "ultimately the most immediate way to tackle air pollution would be to achieve a much reduced number of vehicle kilometres travelled". This requires, it says, behavioural change through other means that can encourage mode shift to more active travel.

To read further reaction to the Government’s draft plan from a local authority perspective click here.