Car manufacturers which try to cheat emissions rules could face unlimited fines under a new crackdown proposed by the Government.
The planned penalties come after the Volkswagen emissions scandal, when the German motor giant was found to be using so-called "defeat devices" to ensure its diesel cars passed laboratory tests of polluting emissions.
The fines cannot be imposed retrospectively on VW, but would expose manufacturers in future to criminal charges for selling new vehicles containing software designed to deceive emissions tests in the UK.
Launching a consultation on the measures, Transport Minister Jesse Norman said: "We continue to take the unacceptable actions of Volkswagen extremely seriously, and we are framing new measures to crack down on emissions cheats in future.
"Those who cheat should be held to proper account in this country, legally and financially, for their actions."
Ministers said the new powers go above and beyond EU requirements, and would extend to any importer bringing a non-compliant model into the UK.
More than 1.2 million vehicles in the UK were affected by the VW scandal, which led the Department for Transport to set up a testing programme for the most popular diesel vehicles on British roads.
No other manufacturers' vehicles failed the tests.
Alongside the consultation, the DfT also announced new anti-pollution measures including:
- Requiring information on the fuel economy of new cars to include results from a new, more rigorous laboratory test cycle;
- Improving the environmental performance and safety of specialist and modified vehicles;
- Implementing stricter rules on the sale of vehicles in stock that do not adhere to the latest emissions rules.
The Government is already committed to ending the sale of conventional new diesel and petrol cars and vans by 2040.