Advertising agency PHD has clinched a media account worth £16 million to mount a major campaign supporting the congestion charging plans.
With a proposed daily fee of £5 per day per car to enter charging zones between 7am and 7pm, Transport for London (TfL) needs 3.2 million cars to pay the charges to cover the cost of advertising alone.
TfL estimates that currently about 250,000 vehicles make 450,000 movements into the zone during the working day, and predicts that the scheme will cut traffic levels inside the charging zone, measured in 'vehicle kilometres', by 10-15%.
The advertising account was previously about £9 million, but could double as part of a media blitz to win public approval for the scheme, which has come under fire from politicians and pressure groups.
Winning public support for the scheme is vital to ensure its success and the level of spending could forewarn other cities of the potential cost of introducing such schemes.
PHD, which has held the account since 1999, will be focusing on the environmental benefits of the scheme that aims to slash the number of journeys into London each day.
The advertising spend revelations are certain to add to the growing concerns over the shape of the scheme, which were extended this week with a stinging attack from Westminster City Council. Charles Cronin, Westminster City Council cabinet member for transportation and infrastructure, said the council was 'extremely concerned' that the TfL consultation document failed to address a number of core issues.
He said: 'We have grave concerns that if it goes ahead in its present form, Londoners will be faced with a transport system brought to its knees.'
TfL rejected his claim, saying a long period of consultation allows all residents to make any concerns or comments heard. A TfL spokesman claimed estimates of an £18 million advertising spend were 'on the high side', but added that drivers had to be properly informed for the scheme to be a success.