One of my abiding memories of Boris Johnson as mayor was his explaining how his technical fix for air pollution worked by spraying the air, capturing the pollution and forcing it to the ground where, if you wanted to, you could snort it up like some toxic cocaine. He got very tetchy when I exposed how his sprayers were focusing their attention around the air pollution monitors and thereby cheating on the official figures for pollution, while leaving most Londoners to breath dirty air.  

It was typical Boris bluster. Find a gimmick, put on a show, don’t worry about actually fixing the problem. He did it time and again as London mayor. He will do it as prime minister with the climate crisis and put all our futures at risk. Don’t believe me? Look no further than Johnson declining to participate in Channel 4′s Climate Change debate, which will see party leaders take questions on the issue, to confirm what we already know.

Air pollution accounts for around 4,000 premature deaths a year in London. It is a public health emergency, but never treated that way by any government whether they are Labour, Coalition or Conservative. Mayor Johnson wasn’t the only politician to be complacent about the impacts on human health, with asthma, hearts attacks, Alzheimers and reduced lung size, all linked to pollution. However, Johnson went out of his way to disguise that complacency with the distracting hum of activity.

Along with the spraying machines. Johnson had pot plants “to absorb pollution” along one of the most polluted roads near the river – no, I’m not making this up. More substantially, he also planted 20,000 street trees in his eight years as mayor. Mature trees are great at soaking up pollution in the summer and keeping a city cooler. Saplings less so. Another of my memorable moments on the London Assembly was explaining to Johnson that one his main delivery partners, Transport for London, had indeed planted 525 trees on its road network in 2009, but it had cut down 853 – a net loss of 328 trees. The same pattern was repeated in several boroughs who lost more trees than Johnson gave them money to plant.

Another typical Johnson ploy was his vision for an Ultra-Low Emission Zone that would discourage all but the cleanest and zero emission vehicles from entering London from 2020 onwards – implemented by the next mayor. Watch out for this one, he will use it a lot if he becomes prime minister. He launched this idea while ditching his predecessor’s plans to take immediate action against the most polluting white vans, just as the number escalated with the growth of Amazon, Tesco and a host of other online delivery companies.    

During the periods of heaviest air pollution mayor Boris did nothing to warn Londoners. He followed the government policy of staying silent about air pollution episodes in a deliberate attempt to minimise the issue. A study of a 10-day episode in 2014 found an extra 300 deaths and 1,600 hospital admissions. Despite the regularity of such deadly episodes, Johnson refused my repeated requests to do more to tell commuters, or health professionals. His successor as mayor, Sadiq Khan, has broken ranks with the government and does issue warnings, but that is still far short of taking measures to reduce the traffic on the roads during those episodes.

Boris Johnson as prime minister, supposedly leading on the climate emergency, will waste five years on gimmicks and inactivity. He will also push through projects that make things worse. Rather than sitting in front of the bulldozers as promised, prime minister Johnson will give Heathrow expansion the go-ahead and start building the single most environmentally damaging project in the UK. Please don’t elect this man.

Baroness Jenny Jones is a Green party peer.