Darren Johnson: We've gone backwards in the fight to clean up

London's air pollution is the worst in the country and among the worst in the EU. Since being elected to the London Assembly a decade ago, I have been warning about the prospect of massive EU fines if we did not get to grips with air pollution in the capital. Ten years on, the EU Commission is pursuing legal action because of London's failure to reach targets on air quality. It is not just a matter of a £300m fine. Leading health experts believe there are 3,000 premature deaths in London each year as a result of air pollution.

Why was our capital city allowed to get into this mess? The previous mayor, Ken Livingstone, did not act quickly enough. But, to be fair to him, we did at least see measures being introduced: congestion charging, a London-wide Low Emissions Zone which set more stringent emissions standards for buses, taxis and lorries, and a traffic reduction policy.

However, even Transport for London's own calculations showed that these would not be enough to bring London's air quality in line with EU targets. One would have assumed, therefore, that the new mayor, Boris Johnson, would have spent the past two years looking at what was needed. Instead, the opposite has happened. He has cancelled or delayed measures that the previous administration introduced. The western zone of the congestion charge is about to be scrapped. The third phase of the Low Emission Zone, which was to apply to vans, has been delayed by two years. The six-monthly pollution checks on black cabs has been scrapped.

The mayor made some rash policy commitments during his election campaign but he now needs to start thinking about the realities of air pollution. It is a matter of life or death.

Darren Johnson is a Green Party member of the London Assembly. He chaired the assembly's investigation into air quality in the capital, "Every breath you take"