Audi has developed a new diesel engine for its A3 line-up which has a carbon dioxide output of 119g/km, making it exempt under the proposed changes to the London congestion charge.
Audi says the new 1.9 TDI engine in the A3 will also return 62.7mpg on the combined cycle.
Prices start at £16,660 on-the-road for the three-door and rise to £17,160 OTR for the five-door Sportback.
Customers can order now for deliveries in early October.
Audi said it would be developing more efficient versions of the rest of its range in the near future.
Transport for London still intends to link the congestion charge to car carbon dioxide emissions. Models which emit under 120 g/km CO2 or less will be exempt, while those over 225 g/km will pay £25 a day to enter the recently enlarged central London zone. Most other cars and commercial vehicles will still pay £8 a day.