Prepare yourself for a shock – the best four by four by far is not as tough as everyone thinks.

The 2004-09 Land Rover Discovery III has come bottom of a reliability index showing that despite its rugged looks and go-anywhere appeal, owners are more likely to be stranded at the side of the road rather than climbing a Scottish mountain.

Warranty Direct analysed around 20,000 live policies on European cars aged three to six years for its index, and found that 85 per cent of third-generation Discos recorded a fault in the last twelve months. Axle and suspension problems accounted for 42 per cent of claims by Warranty Direct customers.

Luxury cars fared just as badly as the British off-roader. The 2003-10 Bentley Continental GT narrowly missed out on the bottom spot with 78 per cent of cars covered by Warranty Direct failing.

The now-deceased Renault Espace was third from bottom thanks to an incident rate of 78 per cent, while the 2002-11 Mercedes-Benz SL gave 67 per cent of Warranty Direct customers problems.

The top ten list of Europe's most unreliable cars included the 2005-10 Range Rover Sport; 2004-09 Renault Grand Scenic; 2002-12 Saab 9-3; 2001-08 BMW 7 Series; the Mercedes-Benz CLS of 2005-2010 and the 2002-09 Renault Megane.

At the other end of the spectrum, the 2006-09 Mercedes-Benz E-Class topped the survey with just one in ten Warranty Direct customers reporting faults.

Skoda builds the second most reliable used European car, the Fabia (2007-) – only 15 per cent of owners will be paying for repairs each year – while the Smart ForTwo (2007-) sits in fourth in the index with the Volvo C70 (2006-) in fifth.

Warranty Direct managing director, Duncan McClure Fisher, said: "It is very interesting to see the Mercedes at the top of the pile for European cars. It's big and it's packed with technology, which is not usually the recipe for a reliable car, but it's proved to be excellent.

"Running a car is more expensive than ever, particularly when it moves into its fourth and fifth year and most cars leave the protection of a manufacturer warranty. If you do your research though and buy the right car or at least protect yourself with a warranty, you're in a much better position."

Top ten most unreliable European cars
Land Rover Discovery III (2004-09)
Bentley Continental GT (2003-10)
Renault Espace 2003-11
Mercedes SL (2002-11)
Range Rover Sport (2005-10)
Renault Grand Scenic (2004-09)
Saab 9-3 (2002-12)
BMW 7 Series (2001-08)
Mercedes-Benz CLS (2005-11)
Renault Megane (2002-09)