The RAC says that Leadsom plans on creating 35 "clean air zones", including Leeds, Nottingham, Derby, Birmingham and Southampton.
The zones would target the worst-polluting cities and it is believed that private diesel vehicles could face restrictions on driving in peak hours, and even daily charges. These measures are aimed at discouraging diesel motorists from driving offending cars into the designated areas.
The new 'toxins tax', which could cost drivers £20 a day, could affect as many as 10 million diesel cars. The very newest models are expected to be exempt from the charge.
A trial is currently underway to charge diesel vehicles £7.35 an hour to park in parts of central London and London Mayor Sadiq Khan plans to introduce a £12.50 per day charge for the most-polluting vehicles entering any part of Greater London.
However, Leadsom's plans would affect the wider country. Reports suggest diesel cars and commercial vehicles in around "nine or 10" of the affected cities could face peak-hour bans, while 25 other towns would only focus on commercial diesels, including coaches, lorries and taxis.
With the creation of a network of clean air zones, local councils would be able to impose bans or charges on polluting vehicles that enter the zones through the use of cameras.
Plans to launch a new diesel scrappage scheme have reportedly been shelved by ministers as they were found to not be financially viable.
Do you agree with the introduction of clean air zones in cities?