The Government has today opened the way to the possible introduction of nationwide charges for the use of roads.

Transport Secretary Alistair Darling produced a feasibility study into the scheme that could - eventually - see drivers having to pay to use major routes.

But he admitted that although such a scheme was being introduced for lorries, a plan for cars presented a major challenge. Mr Darling told MPs today: ''Clearly there's a world of difference between a scheme for 430,000 lorries and one for 26 million cars. No country in the world has done anything on such a scale before.

''And technically this is an entirely different proposition to congestion charging in London, for example, where a charge is paid to drive within a boundary.''

He went on: ''There are many issues that need to be addressed - such as the protection of privacy and whether such a scheme could work technically. Which is why the time has come to set up a feasibility study to investigate these issues in detail.

''Last month my (transport) department held a seminar for motoring, business and environmental groups and others to look at the issues. It was clear that for a scheme to be sustainable in the long term, there needs to be a consensus - not just politically but a consensus across the country.

''So today I am publishing a discussion paper looking at managing roads to get the best out of the road space we have; the possibilities opened up by new technology; and getting the right balance between additional capacity and measures which ensure benefits are ''locked in'', whether through physical measures or pricing.''

Mr Darling continued: ''Our objective must be to provide a better deal for the motorist. Road pricing would be a radically different approach. But it could have huge potential to reduce congestion, to allow faster more reliable journeys, giving motorists a better choice about how and when they travel.

''We'd be failing future generations if we did not test its feasibility and examine the gains that could come from it.'' The feasibility study said a road user charging scheme would have to: Deliver higher economic growth and productivity for all regions of the UK; Be fair, respect privacy and promote social inclusion and accessibility; Deliver environmental benefits; Deliver a more efficient approach to the structure of transport pricing.

The report said that no country had produced such a scheme but it was now ''increasingly realistic to consider the possibility of a future road pricing regime''.