A pay-as-you-go road pricing scheme to cover the whole of Greater London has been proposed in a Green Party-commissioned report.

To replace the inner-London congestion charge scheme, road pricing would cost motorists an average 20p per kilometre (about 32p a mile) and would reduce traffic by about 10%, the report said.

Covering all the London boroughs, the scheme would raise about £3.9 million a day and about £1.4 billion a year.

Prepared by academics, the report was commissioned by the Green Party and will now be sent to London Mayor Boris Johnson. Copies will also go to the London Assembly and to Transport for London.

The report said further investigation and debate would be needed before making decisions about what time of day and what roads to charge for, the level of charge and which vehicles would be exempt.

There were a range of modern technologies which could be used, based upon "greater levels of automation and satellite communications".

Concerns about fairness, social justice and the impact on small traders would all need to be addressed.

The report's authors said: "Put in very clear language it is our view that a London-wide road pricing scheme is essential and without it congestion will worsen and air pollution will worsen.

"The legal consequences of failing to meet air quality standards will grow in severity, the health of Londoners will suffer, CO2 reduction targets will be missed and London will stand no chance whatsoever in achieving `best in class' status that it so richly deserves."

They added: "If this scenario unfolds in this way the consequences will be more severe still because competitor cities are not marking time. They are racing ahead. Almost every major European city is already achieving the success that London may find elusive and the gap will widen and London will slip further down the rankings at an accelerating pace with unwelcome consequences for jobs and inward investment."