The Ford Fiesta ECOnetic and the van version bearing the same eco-signature both qualify for the exemption because of a change to the law allowing all vehicles that emit less than 100g/km to qualify.
This means the 98g/km diesel models will be free to enter the congestion charge zones from next year.
Jon Wellsman, sales director, Ford of Britain, said: “Ford offers a large range of cars and commercial vehicles and I am delighted that they include vehicles which will be exempt from the London Congestion Charge."
The Fiesta and Fiesta Van fit all of the criteria, including complying with the new Euro 5 engines emissions law, which comes into effect in 2011.
Under the new rules, electric cars will also be exempt from the congestion charge, meaning Ford will soon boast four models which will not be required to pay the charge.
"Even more exciting is the introduction of our zero-emission Transit Connect Electric in 2011 and Focus Electric in 2012," said Wellsman.
Electric cars offer zero tailpipe emissions when driven, although they are usually charged using electricity from the national grid.
Previously all hybrid, electric and alternatively fuelled vehicles were exempt from the London congestion charge, but the law was changed to focus on the level of CO2 emissions instead.
Ford’s ECOnetic signature has been introduced to reduce CO2 emissions from Ford’s diesel engine. It means the supermini can compete with the likes of the Fiat 500 and Citroen C1 in terms of emissions, despite being a larger and more powerful car.