The Toyota Auris Hybrid will emit just 84g/km of CO2 from next month.
The hatchback has undergone aerodynamic and tuning enhancements to reduce its CO2 rating by 3g/km, making it the cleanest car in its class.
Toyota has made tweaks to the car's engine control unit, and enhanced the aerodynamics with a new fin on the rear window. The changes apply only to the entry-level Icon trim the Excel version's CO2 figure remains unchanged at 91g/km.
The enhancements will also be applied to the Auris Touring Sports estate when it goes on sale later this summer. It will have CO2 emissions of just 85g/km and will cost from 21,095.