It is the perennial problem presented by green taxes: if they are successful they lead to diminishing revenues for the Exchequer as people switch away from the polluting behaviour that attracted environmental levies in the first place.

New research sponsored by the RAC’s policy arm has today warned against the impact of precisely this phenomenon, estimating that the Treasury could see a £13bn decline in fuel duty and Vehicle Excise Duty (VED) revenues by 2029 as a result of improving vehicle fuel efficiency and more electric vehicles hitting the country’s roads.

The report predicts that as a result companies could find themselves paying to use certain routes if the government decides to use road pricing to compensate for the predicted fall in motoring tax revenues that will occur as cars become greener and more efficient.

Around 65,000 cars sold last year were excused VED by virtue of having CO2 emissions lower than 100g per kilometre and this trend is set to accelerate as fuel prices rise and manufacturers increasingly invest in hybrid technologies, electric cars, and more efficient internal combustion engines.

Emissions from new cars sold in the UK last year dropped to 138g/km, and the country is well on course to meet the EU target of 130g/km by 2015.

While electric cars have been slow to take off, the Committee on Climate Change estimates 60 per cent of new car sales in 2030 will be electric. In the meantime, manufacturers are confident new plug-in hybrid models such as the Vauxhall Ampera, the UK cousin of the Chevrolet Volt, will help spark demand by allowing customers to travel further than in pure electric cars alone.

Making up the tax revenue shortfall would require a 50 per cent hike in fuel duty, which the Institute for Fiscal Studies (IFS), the think tank that conducted the research on behalf of the RAC, notes would be very difficult politically.

The report concludes that pressure on vehicle and fuel tax revenues will help make a “compelling” case for road pricing, considering revenues would not be eroded as cars become more efficient.

The IFS acknowledged that the concept is likely to meet a hostile public reception, but maintains that relatively simple road-pricing systems targeted at the most congested areas would deliver significant benefits.

Although the government has ruled out tolls on existing roads, pricing is thought to have some backing in Westminster.

David Cameron has suggested private money could be used to improve the road network, while a government feasibility study into new “ownership and financing models” for roads is due to report later this year.