Mayor announces plans for Ultra Low Emission Zone
13 February 2013 Last updated at 20:05 GMT
If you want to drive into central London in future you may have to buy a new car.
London's mayor Boris Johnson has announced plans to improve the quality of the city air as the capital regularly breaks European pollution laws and faces fines running into hundreds of millions of pounds.
Mr Johnson wants to allow only the very greenest cars into central London during working hours but it is already being criticised.
BBC London's Karl Mercer spoke to Mr Johnson, Prof Frank Kelly from London's King's College, Steve McNamara from the Licensed Taxi Drivers' Association and environmental lawyer Alan Andrews.