Steven Norris told public sector fleet representatives last week that workplace charging might be a more effective system than the congestion charging due to be introduced in London in 2003, which is expected to cost fleets millions of pounds a year.
Buses, motorcycles and licensed taxis are among the vehicles exempt from charging, while residents within the charging area will pay a daily charge of 50p instead of £5.
Norris said measures were needed to reduce traffic in London, but added that congestion charging was likely to introduce problems as drivers used alternative routes to avoid charging areas.
He told delegates at the First National Vehicle Holdings Agenda for Action conference: 'This is the most regressive form of taxation possible. It's roads-for-the-rich and will hit low-wage earners hardest.
'People will only support it if the money is spent within the charge area and if it is additional money and does not replace funding from elsewhere.
'Workplace charging would be more effective because it would address the 'problem' drivers - those who go by car because they know there is a parking space for them - and would be easy to collect.'
However, he warned against telling people that using public transport was morally superior, because it would result in hostility to change.