The transport secretary, Alistair Darling, last night sent a fresh shiver down the spine of motoring lobbyists when he predicted that satellite technology could soon allow the government to impose congestion charges on car owners.

"We are some way down the road to looking at the technology," Mr Darling told the Sunday Times, pointing out that 450,000 foreign lorry drivers working in Britain were soon to face satellite-based moni toring. The AA and other lobbyists immediately protested.

"If you accept that principle with lorries it seems difficult to see why you shouldn't have a discussion about cars," Mr Darling said.

In effect road pricing could be refined from the proposed £5 daily charge to enter central London into a system for discouraging the use of busy roads at busy times.

In a recent interview Mr Darling said: "No one is anti-car but _ there comes a point when we cannot all drive into a city."