New Mercedes-Benz A-Class saloon to rival four-door Audi A3

Both come as standard with a six-speed manual gearbox, although, as with the hatchback, a seven-speed dual-clutch automatic 'box with steering wheel-mounted shift paddles is an option.

When mated to the latter, the petrol engine is claimed to return combined fuel economy of 54.3mpg and average CO2 emissions of 119g/km, while the diesel records 70.6mpg and 107g/km.

Together with standard front-wheel-drive versions of the A-Class saloon, Mercedes also plans to offer a limited number of four-wheel-drive 4Matic variants, including A35 4Matic and Mercedes-AMG A 45 4Matic models from its AMG performance division.

The A-Class saloon adopts the same front-end styling treatment as the A-Class hatchback, with a prominent grille and angular headights that taper into the leading edge of the front fenders.

It’s only behind the B-pillars that saloon differs from the hatchback, with a longer roof, longer rear doors and a longer rear overhang to accommodate a short, separate boot.

At 4549mm long, 1796mm wide and 1446mm tall, the saloon is 130mm longer, the same width and 6mm taller than the hatchback, with an identical wheelbase of 2729mm.

In comparison, the Audi A3 saloon measures 4458mm long, 1796mm wide and 1415mm tall, with a 2637mm wheelbase.

Mercedes says a relatively small frontal area and the extended rear overhang of the saloon makes it highly aerodynamically efficient. It has a Cd of 0.22, beating the 0.23 Cd of the firm’s previous aerodynamic production champion, the CLA.

Inside, the A-Class saloon features the same dashboard and advanced infotainment functions as the new hatchback, including Mercedes' new MBUX infotainment system with touchscreen control and speech recognition.

Mercedes claims the saloon offers above-average shoulder, elbow and head room for front seat occupants and class-leading head room for those in the rear. Its 420-litre boot capacity, however, doesn’t quite match the 425 litres of the smaller A3 saloon.

The A-class saloon is built on Mercedes-Benz’s MFA II platform and, as with the hatch, utilises two rear suspension layouts: a torsion beam arrangement on cheaper models and multi-link system on higher-end variants.

The model will be built at Mercedes' Rastatt plant in Germany and in Aguascalientes, Mexico, at a new joint venture factory run in co-operation with Renault-Nissan.

The long-wheelbase version for the Chinese market is built at Beijing Benz Automotive in China.