The Liberal Democrats have outlined plans to ban the sale of diesel-powered cars and small vans by 2025 within the party’s general election manifesto, published today.

The party, led by Tim Farron, vowed to implement the plan with the aid of a diesel scrappage scheme and the extension of Ultra-Low Emission Zones to ten more towns and cities.

“All private hire vehicles and diesel buses licensed to operate in urban areas to run on ultra-low emission or zero emission fuels within five years,” the party’s manifesto added.

The Lib Dems also plan to “reform vehicle taxation to encourage sales of electric and low-emission vehicles and develop electric vehicle infrastructure including universal charging points”.

Alex Buttle, director, car buying website Motorway.co.uk, was quick to question the party’s plans for diesel vehicles. Buttle said: “A total ban on diesel cars is likely to be highly unpopular for the car-owning electorate - 39% of which own diesel vehicles. And the value of diesel vehicles would tumble immediately if this policy was put into place.

“Everyone now knows diesel cars are high-polluting, although car owners were encouraged to buy them for their fuel efficiency a decade ago.

“A rapid phase-out of new diesel cars makes sense, but that shouldn't extend to used diesel vehicles, to protect the personal finances of UK drivers.”

The current Conservative government’s clean air plan – likely to include the creation of clean air zones within which authorities could charge a “toxin tax” to the worst emitting vehicles – is due to be published by July 31.

Details of a "targeted" car scrappage scheme were featured in technical documents supporting the main consultation paper, detailing a possible £8,000 incentive to 15,000 owners of the UK’s most polluting cars to make the move to EVs.