That warning came as two transport academics published a report claiming charging drivers per mile would yield substantial economic benefits.
Imperial College's Stephen Glaister and Daniel Graham said road pricing 'looks a more promising tool than any other on offer'. But they said it would be hard to win public acceptance for road charging, and suggested a regulator would be better trusted than politicians to set fair prices.
The government has created the transport innovation fund, due to be worth£2.5bn by 2014-2015, largely to support councils in charging schemes.
'Are they doing it to spread the load of traffic during the day, to achieve shift from cars to public transport or to encourage traffic onto other routes?'
Public support would depend on an understanding of the objectives and provision of high quality public transport alternatives.
'You have to get the Mercedes driver onto public transport, not just improve it for existing users,' Mr Chorlton said.
He predicted road pricing would prove 'part of the package but not a magic bullet', in curbing traffic growth.