Sadiq Khan has said cars should be banned from roads near schools in order to reduce air pollution.
The mayor of London accused the Government of “ignoring” toxic air and criticised Philip Hammond for not raising taxes for the most polluting vehicles in Wednesday’s Budget.
It comes after a recent study found that tens of thousands of children in London's schools are exposed to illegal levels of air pollution that can damage their health permanently.
In an interview with the Times, Mr Khan compared politicians who overlook air pollution to those who were aware of the health risks of smoking 50 years ago but did nothing.
He said: “The reason why I’m so angry about this and it’s a priority for me is that the science and the evidence is unarguable and yet it appears the government is ignoring it.
“Forty or fifty years ago we thought smoking was bad and yet our forebears took no action. We know air quality is a killer, it makes you sick and no action has been taken. It’s a health emergency.”
Labour’s most powerful elected politician wants more parents to walk their children to school in order to reduce the number of cars on the roads.
Camden council and the City of London have already banned traffic from some roads around schools and he wants the other 30 boroughs to follow suit.
“You can’t play politics with people’s lives and people’s health,” said Mr Khan. “Every day action is delayed it means another young person breathing in this toxic air, an older person having breathing problems because of the poor quality of the air and literally people die.
“Why can’t we work with schools and councils to have some roads outside schools where cars aren’t allowed to go? Really encourage mums, dads, carers and children to walk to school. It will be safer and you are not breathing in toxic air when playing in the playground.”
However, the mayor stopped short of supporting a full ban on diesel cars, which has been proposed in other European capitals including Paris and Madrid.
He said an outright ban would be “simplistic” and “crude”.
“There is no road map for how they get from here to banning diesel,” he added. “Some of the new diesel is better than some of the old petrol.”
A report published in February, commissioned by the mayor, found that pupils at 802 of the capital's schools are routinely breathing in toxic air that increases their chances of developing conditions such as asthma.
The report also shows that London's poor are far more likely to be living in areas affected by air pollution linked to 9,000 early deaths every year in the capital.
It is one of many places hit by the UK's air quality crisis, which has caused the Government to be issued with a "final warning" by the European Commission for repeated breaches of legal limits.
Mr Khan has has already announced the introduction of a £10 "toxicity charge" for drivers of some of the oldest and most polluting cars in central London from October.
London is not the only city affected by the air quality crisis.
Birmingham, Derby, Leeds, Nottingham and Southampton are also planning to charge for the highest polluting vehicles to enter clean air zones.