Previously only alternatively fuelled vehicles such as electric or hybrid cars were eligible for the exemption, but from 4 January all cars with CO2 emissions under 100g/km will not be forced to pay the charge.
This means owners of petrol and diesel cars can now enjoy the benefits of not having to pay the charge levied at all cars entering the London area.
For Citroen owners, the new C3 supermini boasts a 99g/km model while the more premium DS3 supermini also comes with an exemption to the charges for 2011.
Linda Jackson, Citroën UK Managing Director, said: "The two Citroën models now exempt from the congestion charge demonstrate that a greener choice does not mean compromising on style, comfort or driving pleasure."
Both cars also comply with European air quality laws, named Euro 5, and therefore match all of the criteria for the exemption.
Other cars to now qualify for the exemption include the new Fiat 500 TwinAir, one of the only petrol models to boast sub-100g/km emissions, and certain models from the Ford Focus and Fiesta ranges.
The Seat Leon and Ibiza will also be eligible for free driving in the capital if the Ecomotive 1.4-litre diesel Ibiza or the 1.6-litre diesel Leon are chosen.
However, electric cars will still qualify for the exemption, although some hybrid cars with emissions over 100g/km will now have to pay the full congestion charge.
This means the likes of the Citroen C-Zero and Peugeot iOn, both released in January 2011 on leasing deals, will be exempt from the London Congestion Charge.
In a further bonus to drivers of sub-100g/km cars, all cars qualifying for the congestion charge exemption also benefit from zero Vehicle Excise Duty (VED) because it is based on CO2 emissions.