Sadiq Khan says Government proposals to cut nitrogen dioxide pollution don't go far enough.
The Government has published its draft air quality plan after being told to do so by the High Court.
It includes a proposal to encourage motorists to scrap polluting cars. But the London mayor described the plan as "inadequate" and says a new Clean Air Act is needed to get the capital's pollution within legal limits.
The Government is consulting on a range of measures including the option to introduce clean air zones in 27 towns and cities in England to reduce pollution in urban areas.