Speaking to the Evening Standard, Transport Secretary Patrick McLoughlin said it had been a “mistake” for former Labour chancellor Gordon Brown to slash taxes on diesel, leading to a dramatic increase in the number of diesel cars being run, and hinted that diesel taxes could be raised.

Mr McLoughlin said: “It's something that we've got to address. We are addressing it through the Government's air quality strategy, and by putting money into public transport like the Elizabeth line.”

His comments come just weeks after new London Mayor Sadiq Khan announced plans to launch a consultation on measures including bringing forward the start data for London’s Ultra-Low Emission Zone (ULEZ) and extending its reach, as well as implementing an extra charge on the most polluting vehicles entering central London and setting up a diesel scrappage scheme.

Earlier this year, proposals including increasing and extending the 3% diesel surcharge and removing or reducing the capital allowances for diesel vehicles were set out by think-tank Policy Exchange as part of a package of measures to tackle air quality in London and in the UK overall.

In response to the Transport Secretary’s comments, RAC spokesman Simon Williams said: “The present tax system has for many years favoured diesel over petrol vehicles, not least because diesel cars generally emit lower levels of CO2. Many drivers and businesses have, in good faith, invested in diesel cars for this reason. What is more, diesel drivers contributed almost £17bn in fuel duty last year and already pay some of the highest diesel prices in Europe.

“There is no doubt that action is needed to improve air quality, however by the Government's own admission this needs to be tackled at a local level. This is something clean air zones, proposed for a number of UK cities, can help address. Additionally, incentivising motorists to take up cleaner vehicles additionally is important.

“But there must also be a concerted effort to clean up older, more polluting bus and taxi fleets in towns and cities. The Government can also not ignore the fact that congestion levels can exacerbate pollution levels and must consider measures that keep traffic moving.”