The government’s plan to ban the sale of diesel and petrol cars is not sufficient to combat air pollution in north Kent, according to a transport campaigner who is pushing for a public tram system connecting the county with Essex.

Last week environment secretary Michael Gove announced proposals that would see only electric models permitted for purchase from 2040.

Councils in Kent are to be given a share of a £255 million pot of money to curb pollution caused by traffic on their busiest routes, with Mr Gove not ruling out the idea of charging on the most polluted roads.

But with Dartford and Gravesham suffering some of the highest nitrogen dioxide levels in the UK, James Willis, one of the main drivers behind KenEx Thames Transit, said more needed to be done.

“The report passes the buck to local councils who are offered a tiny budget to fight it out for,” said Mr Willis.

“This does not offer anything to those residents who have unwittingly bought diesel cars in the last decade based on government incentives and fudged pollution figures from car manufacturers.

“A diesel scrappage scheme is required now, combined with investment in clean and efficient public transport.”

The proposed KenEx tram scheme would run under the River Thames from Grays and draw 10% of traffic away from the Dartford Crossing, which government figures show will be operating at an estimated 120% capacity by 2025.

Mr Willis believes more investment in public transport is vital in combating air pollution, with the price of electric cars so far putting motorists off.

Over the weekend electric car maker Tesla, which has a showroom at Bluewater, rolled out its new Model 3 vehicle — the company’s cheapest car to date.

Tesla chief executive Elon Musk said the Model 3 was the “best car for its cost, either electric or gasoline”, but prices start at more than £26,000.

Dartford Labour leader Cllr Jonathon Hawkes said the government should be providing greater incentives for people to give up polluting vehicles.

“This plan is a huge missed opportunity from the government that does nothing to address the pollution Dartford residents face every single day,” he said.

“A proposed diesel scrappage scheme, which would incentivise drivers to give up polluting vehicles, has been watered down – leaving millions of polluting vehicles still on the road.”

His view was shared by South East Green MEP Keith Taylor, who has opposed the government’s plan for the Lower Thames Crossing east of Gravesend.

Earlier this year, environmental group Friends of the Earth warned that people in Gravesham were already being exposed to excessive levels of nitrogen dioxide.

Mr Taylor said: “The proposals fail to acknowledge that by 2040 there will be more than 40 million petrol and diesel cars on our roads completely unaffected by the ban.”