Spied: Audi A7

The long, low four-door Audi A7 has been spied testing in Germany ahead of its launch in 2010.

The Audi A7 will slot into the range below the A8 and above the A6, providing Audi with a rival for the Mercedes-Benz CLS.

Our spy pictures show the A7’s size and sleek styling, especially around the rear, where the car has a high rear deck and a low, steeply raked rear roof line. The coupé-style lines help to disguise the car’s bulk; it’s 4.8m long.

>> See spy shots of the Audi A7

Underneath the unusual bodyshell is the platform that will form the basis of the next A6, itself not due until 2011. The A7 is a variant of Audi’s Modular Longitudinal Platform, which was first used in the new A4 and A5.

That doesn’t mean the A7 will be a five-seater, though; the car is expected to offer spacious accommodation for four, like the VW Passat CC.

The A7 is intended to be a range-topper, so don’t expect any four-cylinder versions. The entry-level engine is likely to be Audi’s 2.8-litre petrol V6, although the big seller will be the 3.0-litre V6 turbodiesel (the same engine used in Porsche’s new diesel Cayenne).

S tronic double-clutch and new eight-speed automatic transmissions will be optional; the standard set-up will be a six-speed manual ’box.

Audi is also planning a convertible A7, although it will have to come up with a solution to the structural issues of chopping the roof off a four-door car.

It is possible that an Audi A7 convertible could use a folding hard-top, making it the first Audi to do so. But the firm insists that it will continue to use a fabric roof on its convertibles to save weight and cut complexity.

The A7 is unlikely to come cheap. As joint range-topper with the A8 (due to be replaced next year by an all-new model), its prices should start at around £48,000.