Audi has launched a new version of its A3 hatchback that averages 74.3mpg and emits 99g/km of CO2.

As a result it the cleanest and most economical premium small hatchback on sale.

A start-stop system, smaller 15-inch wheels, improved aerodynamics, reduced ride height and a revised final drive ratio all contribute to the low emissions.

It is powered by a 1.6-litre diesel engine, and achieves the same performance figures as the equivalent standard A3: 0-60mph in 11.4sec and a top speed of 121mph.

To keep weight down, the car is only available as a three-door hatchback, with one trim option and a five-speed manual gearbox.

It costs £18,005 - £500 more than the equivalent standard 1.6 TDI model without the economy tweaks. The standard car averages 68.9mpg and emits 109g/km CO2.

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