Motorists should pay higher taxes in the form of a national road-pricing system to cut carbon dioxide emissions, according to the Government’s climate change advisory body.

The speed limit on all motorways should be strictly enforced and may have to be reduced to 60mph to help to meet the Government’s legally binding carbon reduction targets.

The Committee on Climate Change, which devised the targets and advises the Government on how to meet them, says that a “step change” is needed in emissions reduction. In its first annual report to Parliament , the committee says that emissions cuts since 2003 have been “far slower than now required to meet (carbon) budget commitments”. Emissions fell by an average of 0.5 per cent in each of the five years to 2008. The committee says that emissions cuts of 2-3 per cent a year are needed every year from now until 2050 to meet the targets.

Its most controversial recommendation is that the Government should consider imposing road pricing as an additional tax on motorists. Ministers had previously proposed a revenue-neutral road-pricing system, with the sum raised in per-mile charges offset by reductions in fuel duty. The Government abandoned this idea two years ago after 1.8 million drivers signed a petition opposing road pricing on the Downing Street website.

Now the committee has resurrected the proposal and made it even less appetising for drivers by saying that road pricing should be an additional tax, with no reduction in fuel duty.

The report says: “From an emissions perspective, road pricing should be introduced as a complement to fuel duty rather than a substitute. This conclusion is buttressed by the fact that fuel duty plays a crucial role in providing incentives for purchase of electric cars, increasing electric car cost savings relative to conventional cars.”

It says that by 2020, road pricing could save 5.6 million tonnes of carbon dioxide a year — 5 per cent of total road transport emissions. It says the savings could rise to 15 per cent a year by 2040. The committee concludes: “Road pricing could be a useful component of a strategy for transport emissions reduction, and the committee recommends that this should be seriously considered by the Government.”

It also calculates that rigorously enforcing the 70mph limit would save 1.4 million tonnes of CO2 a year. There are few speed cameras on motorways, and about half of cars exceed the limit.

The committee calls on the Government to consider forcing drivers to install automatic speed limiters, known as intelligent speed adaptation (Isa).

It says that reducing the motorway limit to 60mph would save an additional 1.5 million tonnes of CO2 a year.

Fuel consumption rises exponentially with speed. The report says: “A petrol car driven at 70mph emits around 20 per cent more CO2 per km than when driven at 50mph.” The committee concludes: “Given that the 70mph speed limit is an existing policy, the committee believes that the Government should seriously consider enforcing this, either through the current enforcement mechanism, or through rolling out Isa technology to both new and existing cars.”

It also says the Government may have to double the grants planned for electric cars from 2011 to £10,000 for at least the first 25,000 buyers. It says otherwise the extra cost of battery-powered cars would be prohibitive.

The committee concludes that the total subsidy needed to achieve widespread use of electric cars is likely to be £800 million, rather than the £250 million pledged by ministers.

Britain’s free-market approach to electricity generation is failing to deliver the carbon savings required, the committee reports. It proposes government intervention to raise the price of carbon emissions permits, currently about £12 a tonne. The committee considers this too low to give power companies sufficient incentive to invest in renewable energy. It also says the Government should consider a tax on carbon if the European emissions trading scheme continues to have little impact on total emissions.

The committee calls for 8,000 more wind turbines by 2020, three new nuclear power stations and four coal plants with carbon capture and storage systems. It also suggests a national programme to insulate homes and install efficient condensing boilers.

David Kennedy, the committee’s chief executive, said that the Government needed “stronger levers” to force people to cut emissions. “We have to do six times better than we have done on CO2 reduction,” he said. “We have to have a more forceful policy, and if we do that we can succeed."

Times recommends

• Energy-saving ideas from switched-on professor
• Rooks are as clever with tools as chimpanzees
• Burping of the lambs blows roast off menu