Roads chiefs will block blanket 20mph zones and scrap outer London’s Ultra Low Emission Zone (Ulez) if the Conservatives are re-elected.

Top Tories would table a “Backing Drivers Bill”, which they say would “protect drivers from the draconian policies of local Labour politicians”, the party said in a statement.

With General Election campaigns underway, Transport Secretary Mark Harper said: “We will reverse Sadiq Khan’s unfair Ulez expansion and rule out any blanket 20-mile-an-hour zones because we are on the drivers’ side. And we will rule out any pay-per-mile road tax to keep costs for drivers down.

“There’s a clear choice at this election – Labour who will continue to penalise drivers or the Conservatives who will back drivers.”

Prime Minister Rishi Sunak took aim at Labour leaders in Westminster and Cardiff Bay, who he accused of launching a “war on drivers”.

Drivers of the most polluting vehicles must pay a £12.50 daily charge if they use almost any road within Greater London, on top of any tolls or the inner London Congestion Charge. Drivers of Ulez-compliant vehicles do not have to pay the fee.

According to Mayor of London figures from October last year, 95% of vehicles on the capital’s roads are “compliant with clean air standards” – up from 39% in 2017.

Imperial College London, commissioned by City Hall, found that “toxic air” contributed to around 4,000 premature deaths in the capital.

But the policy proved controversial when Labour Mayor of London Sadiq Khan fronted its expansion to cover outer London boroughs last year – into areas such as Bromley, Croydon, Heathrow Airport and Wembley.

It previously covered the area between the A406 North Circular and A205 South Circular roads.

Vandals are known to have damaged Ulez cameras and signage, while anti-Ulez protesters have gathered on several occasions in Parliament Square, Trafalgar Square and Strand.

The Welsh Government reduced the restricted roads “default” speed from 30mph to 20mph in December last year, in built-up areas including villages, towns and cities.

Labour’s Cabinet Secretary for Transport, Ken Skates, “is undertaking a programme of listening” between April and July this year, according to the Welsh Government, and will produce new policy guidance for the autumn.

“We still believe that 20mph is right, but we want to make sure we are getting the right speeds on the right roads,” a Welsh Government webpage reads.