There are calls for the European Union to ban the making of cars that can go at more than 101mph (162km/h).
The proposal comes in a report to the European Parliament on EU plans for a law to curb CO2 emissions from cars.
MEPs will vote on the plan this autumn but the BBC has seen an early draft of the report, which will be released to parliament later this month.
Its author, British Lib Dem MEP Chris Davies, says 101mph is 25% more than the top speed limit in most EU states.
He says cars have gradually increased in power and weight, which increases their CO2 emissions, even though people cannot legally use that extra power.
His report also suggests that a fifth of car advertisements should be devoted to cars' fuel consumption and CO2 emissions.
The European Commission is preparing legislation that would limit CO2 emissions of the average new car sold in Europe to 130g per kilometre, by 2012.
But a spokesman said it would not support moves to limit the top speed of cars.
Mr Davies says it will be costly for industry to meet the commission's proposed target of 130g/km by 2012, and suggests instead a target of 120g/km by 2015, followed by a second target of 95g/km by 2020.