The Society of Motor Manufacturers and Traders has cast doubt on the latest reliability survey from used car warranty provider Warranty Direct.

The company says that it uses data from the thousands of claims it handles each year to show which vehicles are the most and least reliable.

But the SMMT claims that despite repeated requests from itself and members, Warranty Direct appears unwilling or unable to provide details of sample sizes and methodology to support the survey, and has consequently questioned the validity of the results.

According to the survey, the least reliable vehicle was the Renault Espace (97-02) with a 71% failure rate, followed by the Jeep Cherokee (93-01) and Saab 9-5 both with 55%. The highest rated car was the Honda Civic (99-06) with a 6% rating.

“These are real cars, real claims and genuine bills,” says Duncan McClure Fisher of Warranty Direct, which states that the survey is based on more than 26,000 vehicles built between 2000 and 2002 using a minimum of 100 examples for each model.

SMMT chief executive Christopher Macgowan says: “The statement makes is very difficult for the industry to take the results seriously, and for the media to cover the story accurately.”