Motorists could face constant petrol price rises if recommendations yesterday from a prominent Government advisory body are adopted.

A "steady increase in fuel price is essential to help control CO2 emissions", the Commission for Integrated Transport said in a report.

The price of fuel can be a "significant and visible element of overall costs of road transport", added CfIT in its report to the Government on transport and climate change.

The study contains a raft of recommendations and the commission said its proposed measures would mean that transport emissions would fall against 1990 levels by 14 per cent by 2020 instead of stabilising broadly at 2005 levels.

It also said the new climate change committee proposed by the Government should advise the Government on where and by how much fuel duty may need to increase.

CfIT's climate change working group chairman Michael Roberts, who is also director of business environment at the Confederation of British Industry, said: "This report stands out from others by focusing very much on the cost-effectiveness of measures to cut transport carbon emissions. Our knowledge in this area needs to improve as it is vital to identifying the best economy-wide approach to meeting the UK's reduction targets.

"It has long been recognised that we need to promote technological and behavioural change to secure reductions in transport emissions. This report emphasises the importance of bringing together measures aimed at achieving both.

"The Government's current approach already reflects this but could in our view be developed further to good effect.

"Our aim is to ensure that cost-effectiveness remains a touchstone for policy makers facing the difficult yet necessary choices about how best to reduce the impact of transport on climate change."

Responding to the report, AA public affairs head Paul Watters said: "We have seen many motorists try to offset the impact of higher fuel prices by buying diesel cars and smaller cars. However, the switch is expensive, costing around £1,000 more to buy a diesel model, and inappropriate for most drivers, such as families who need bigger vehicles.

"Huge improvements in engine and fuel technology have kept CO2 emissions from passenger cars at virtually the same level as 10 years ago, despite the addition of 5.8 million more of these cars in the same period. Hiking up fuel prices adds pain with little or no gain.

"The Government knows how much drivers hate sitting in congestion, watching fuel disappear out of the tailpipe. However, we have been here before - the advocates of pricing people off the road continue to fail to recognise that we don't have a transport system to match those in Europe."

Friends of the Earth's senior transport campaigner Tony Bosworth said the proposals were "a step in the right direction but don't go far enough".

"Plans for teaching eco-driving are a good idea," he said. "But we need tougher targets for emissions from new cars, greater investment in alternatives to driving, and cuts in spending on road-building. The Government must start making these changes in next month's pre-Budget and comprehensive spending review.

"Plans to tackle aviation through emissions trading will have little impact unless they are dramatically strengthened. The Government must include international aviation emissions in its proposals for a new climate change law and stop airport expansion."

Paul Smith, founder of anti-speed camera group, said: "The Department for Transport and their advisers should be very ashamed of themselves. Road safety requires clear and consistent messages.

"We need drivers who concentrate on remaining safe rather than a whole range of fairly spurious other factors. We need drivers who plan well ahead. Planning well ahead is the essence of safe and economical driving."

A Department for Transport spokesman said the Government was taking wide-ranging action and its approach agreed with much of what was recommended by CfIT.

"CfIT's report is a welcome contribution to the debate and we will consider it carefully," he added.

The CfIT report says:

* There should be greater adherence to the 70mph limit on the roads. Enforcement of the limit possibly saves about one million tonnes of carbon (MtC) a year.

* Principles of "eco-driving" - such as accelerating smoothly, not braking sharply and not over using air conditioning - might be incorporated into the driving test.

* Road user charging will be "integral to our management of vehicle emissions in the future" but further analysis is needed on the potential to design a scheme to deliver both congestion and CO2 reductions.

* The Government should consider replacing the Air Passenger Duty airport departure tax with an emission charge on aviation fuel when international agreement is reached

* Aviation should be included in the EU emissions trading scheme which would run alongside the aviation fuel charge "to send a clear signal to aircraft operators and air travellers about the climate consequences of their decisions to fly".

* There should be a mandatory EU target that new cars do not emit more than 100gms of CO2 per kilometre by 2020.