Motorpoint predicts that 20 million motorists will be downsizing next time they purchase a new or used vehicle, mainly due to trying to reduce running costs.
The triple savings which superminis and small SPVs can offer in terms of less depreciation, cheaper fuel costs and lower emissions will shift the balance of privately-owned traffic on the UK roads.
Motorpoint managing director David Shelton said: "These figures show a potentially massive shift of over two thirds of the motoring population about 20 million people into smaller vehicles.
"It’s clear that the benefits of a smaller car are becoming more important as a whole range of economic and environmental considerations start to bite."
The newly elected mayor of London, Boris Johnson, is coming under pressure to review the Low-emissions and Congestion charging price bands for travelling in the capital city, following the de-selection of Ken Livingstone, the previous mayor.