Road user charging could cut congestion significantly, but must not be just another tax on motorists, says the CBI.

The employers' organisation welcomed the House of Commons Transport Committee's support for road user charging in its report published today, saying introducing a closer link between costs and use of the busiest routes would encourage more efficient use of the road network.

But the CBI warned, however, some key questions remain.

Michael Roberts, CBI director of business environment, said: "We've estimated congestion costs businesses £20 billion a year. Used with other measures, road pricing has the potential to cut urban congestion significantly, perhaps by as much as half.

"If we're going to change driver behaviour and make more efficient use of the network we need a system that means those who make most use of the busiest roads pay most.

"But businesses would be angry if charging became just another way of raising money for general government spending. They want to know whether the money raised will be returned to them by cuts in other motoring taxes, reinvested in transport improvements or a combination of the two?

"They want to know who will set the charges and how? It is important that any charges vary according to time of day and place.

"And they want a clearer assessment of the economic impact of pushing up transport costs, particularly on peripheral areas of Britain. These questions are difficult and will take time to answer. Work should start now, but they must not be an excuse for doing nothing in the meantime."