Kensington and Chelsea residents marched against plans to expand the congestion charge into their west London borough on Saturday.
Mayor Ken Livingstone wants to extend the £5 road toll westwards, which would also cover more parts of Westminster.
But residents say it would damage their quality of life despite a Transport for London (TfL) survey suggesting 53% of them wanted the charge.
Scores of people carrying balloons joined the march from Holland Park.
The extended boundary would stop just short of Shepherd's Bush to the west, run as far north as Kensal Green Cemetery and down to Chelsea Embankment in the south, and it could be in place as early as 2006.
Bigger residential area
Congestion charging was introduced in February 2003 for people driving throughout an eight-square-mile zone of central London.
It has reduced traffic and journey times but some businesses claim in has damaged trade.
About 3.3m households, 250,000 businesses and 1,400 other bodies have received a leaflet outlining TfL plans for the extension.
The expansion would cover a much more residential area; about 230,000 residents compared to the 150,000 people living in the current zone.
A TfL survey last year suggested over half of residents in Kensington and Chelsea wanted the charge.
Scores of people joined the march on Saturday
But this is disputed by the council, which says the plans split the borough, leaving 20,000 residents outside the zone.
Its survey found 61% of the 1,800 people surveyed gave a "flat no" to any kind of extension and only 2.5% supported the current extension scheme.
Any expansion would only take place after TfL has assessed two years of the current scheme's performance and if Mr Livingstone wins this year's mayoral elections on 10 June.
The mayor is also awaiting the outcome of the Government Spending Review before he can work out how much he has to spend on his transport policies.
He has said there is no "financial case" for an extension to the zone.
It is expected to bring in £10m a year but would cost about £100m to set up.
But he said the remaining part of Westminster and the affected part of Kensington and Chelsea were "pressing cases" for the charge's economic and financial benefits.