When the likes of Jaguar, Porsche, Ford, GM, BMW, Mercedes, Audi, Volkswagen, Renault and Chrysler introduce a new model series, it is equally or more reliable than the model it replaces. Right? Wrong! New information has been released this week which indicates all of the above companies have replaced major models with less reliable models in the last decade - the worst three examples were 60%, 54% and 40% more likely to break down than the model they replaced.

The figures released by Warranty Direct are based on a comparison of frequency of failure across 55,000 vehicles and shows that when the third generation XJ Jaguar replaced the 1997-2003 second generation XJ Series, it was 60% more likely to break down than the model it replaced.

Other glaring examples highlighted by the new statistics are the 2004 Porsche Boxster redesign which was 35.7% more likely to break down than the original model, the Ford Fiesta Mk V (2002-2008) which was 54% more likely to break down than the Fiesta Mk IV (1995-2002) it replaced, and the Vauxhall (Opel) Zafira B of 2005, which was 40% more likely to break down than the Zafira A it replaced.

The statistics were released by well-known UK company automotive warranty company Warranty Direct - as a privately-owned insurance intermediary, the firm collects lots of data about warranty issues - a lot of it is information you'll never find out from the manufacturers. Warranty Direct has taken this data and produced a reliability index - an independent comparison of frequency of failure across the 55,000 vehicles it insures.

The list makes fascinating reading. Cars with impeccable names fare poorly in light of this normally hidden information. We've previously used this data source for numerous stories, including our story on the 100 most reliable used cars of the past decade.

It's a glimpse into one of the most important buying criteria, and it's one of the few places you'll see it, though we should caution the stats relate only to the United Kingdom - it's sheer coincidence that nearly all of the cars in the list are available in multiple international markets.

"Our analysis shows that new doesn't necessarily mean more reliable," said Warranty Direct managing director, Duncan McClure Fisher.

"We also found that repair costs are often higher for new models so, as well as paying over the odds for a new car, you may also be opening yourself up to additional, unwanted costs."

1 - Third generation Jaguar XJ Series 60% more likely to break down

The worst case reported in the statistics was the Jaguar XJ Series, the second most expensive cars on the list, behind the Mercedes CLK. A new XJ sells for between GBP45,000 and GBP94,000 - hardly the sort of car you'd expect would have reliability problems.

The Jaguar XJ luxury saloon car series was launched in 1968, and has been the marque's top seller ever since.

In 2003, the third generation XJ (known as X350) was released to great fanfare. While the car's exterior and interior styling were similar in appearance to the second generation, the new XJ was far more technologically advanced than its predecessor, with a lightweight, all-aluminum body, much better performance, roadholding, fuel economy and lower emissions.

The statistics provided by Warranty Direct indicate that the XJ Series cars produced from 1997 to 2003 had a 35% "chance of failure" in a given year, but following the redesign, the "chance of failure" for the subsequent third generation XJs, those produced from 2003 onwards, rose to 56%.

Now an increase from 35% to 56% likelihood of breakdown is substantial - while the Warranty Direct statistics listed this an an increase of 21% in the likelihood of breakdown for the third generation Jaguars, an increase from 35% to 56% means the third generation Jaguar is actually 60% more likely to break down than the previous model.

The current Jaguar management can point to new ownership, and that the current Jaguar XJ was launched in 2009 and is not included in the figures. It will be interesting to see how it fares in the Warranty Direct figures.

2 - Ford Fiesta Mk V is 55% more likely to break down than Fiesta Mk IV

The second-worst case recorded by the statistics was that of the Ford Fiesta Mk V (2002-2008), which was 54% more likely to break down than the Fiesta Mk IV (1995-2002). To be fair, look at the reliability of the Mk IV and you'll see why it is such a hot seller. It doesn't break down very often - far less than the most expensive car on the list, the Mercedes CLK.

So it isn't just a minor model that became 55% more likely to stop than the one it replaced - the best-selling front-wheel drive compact Fiesta has sold more than twelve million units since 1976 and the exact same car is built in Europe, Brazil, Argentina, Mexico, Venezuela, China, India, Thailand and South Africa.

Warranty Direct reports that the average repair cost for a Ford Fiesta Mk V built between 2002 and 2008 is almost double that paid by owners of a Fiesta Mk IV (1995-2002) model - given that the same car was built the world over, the same lack of reliability was presumably also imposed on a global market.

Indeed, for the average repair cost to nearly double (GBP114.42 to GBP189.80) from one model to the next, the question needs to be asked whether Ford purposefully decreased the reliability a notch to increase the profitability of the model.

3 - Vauxhall Zafira B 40% more likely to break down than Zafira A

Known in the statistics as the Vauxhall Zafira (GM's brand in the UK is Vauxhall), the Opel-designed compact Zafira people-carrier is part of General Motors' world car plan, and has been produced in four different locations (Germany Poland, Thailand and Brazil) for distribution around the world under several different names - the Chevrolet Nabira, Chevrolet Zafira, Holden Zafira and Subaru Traviq, as well as under the Opel brand in Europe, as the Zafira.

The original Zafira (the A model), was based on the mechanicals of another of General Motors world cars, the Astra, and the subsequent model series, the Zafira B which began roll-out in 2005, was also based on the mechanicals of the next generation H/C model Astra.

The original A series (1999-2005) Zafiras had, according to Warranty Direct, a 27% chance of failure, while the current model Zafira B (2005 to the present) has a 38% chance of failure, meaning that the new Zafira is more than 40% more likely to fail than the old one.

Warranty Direct elaborated on the woes of the Zafira, noting that its statistics showed the current model as being around twice as likely as older models to suffer an electrical fault.

4 - Porsche Boxster 987 36% less reliable than the original

The Porsche Boxster was one of Porsche's biggest moves of the 1990s, melding the words "boxer" for its horizontally-opposed engine, and "Roadster" into one car, which would be its biggest seller for the next decade. The mid-engined sports car was very important in that it was the marque's first road vehicle to be originally designed as a roadster since the 550 Spyder.

The first-generation 986 Boxster (the 986) was introduced in late 1996 and was built in a variety of engine sizes as both a base and S model, before being replaced in 2004 by the 987 Boxster series. Warranty Direct lists the original 1996-2004 Boxster series as having a chance of failure of 28%, which increased to 38% for the current series of Boxster produced from 2004 onwards.

That means that the current Porsche Boxster, at least according to Warranty Direct's figures, is 35.7% more likely to stop than an original model.

5 - Post-2005 Audi A4 30% more likely to break down than pre-2005 A4

Based on Volkswagen's B platform, the Audi A4 is a compact executive car introduced in 1994, and now in its fourth generation, with more than five million cars sold. The second generation Audi A4 had a fine reputation for reliability with just a 26% chance of failure according to Warranty Direct, but the subsequent third generation model (produced from 2005 to 2008), was rated a 34% chance of failure - though still in the mid-range on the reliability scale, the third generation Audi A4 was nonetheless more than 30% more likely to fail, with Warranty Direct noting that one in three third generation Audi A4s had engine problems, as opposed to only one in ten of the second generation.

Meanwhile, more recent BMW 3 Series models are three times more prone to picking up brake system problems, with almost one in seven '05-'11 models requiring workshop visits.

6 - Renault's Espace becomes less reliable when manufactured by Renault

Renault's Espace was one of the pioneers of the MPV concept, with the French giant using another famous French automotive company, Matra, to produce the vehicle's first three generations, before redesigning and manufacturing the Espace from 2002 onwards.

The distinctive Renault people carriers manufactured by MATRA performed poorly in reliability ratings, with the third generation achieving a chance of failure in any year of 51% - one chance in two.

When Renault designed and built its own vehicle, the fourth generation, the Renault Espace's chance of failure increased to 62% - in effect, though the original Espace had poor reliability, the current Espace is 21.6% more likely to break down.

7 - Volkswagen's Golf gets less reliable

The front-wheel drive Golf is a small family car introduced in 1974 and marketed worldwide across six generations as the Golf, Rabbit and Caribe - with sales of around 28 million vehicles, the Volkswagen Golf is now one of the largest selling models of all time - it even outsold the Beetle, the car it replaced in the model line-up.

The Golf Mk IV was produced until 2004, and was followed by the Golf Mk V, which was introduced over the next few years in Volkswagen's global network. According to Warranty Direct, the Mk IV Golf had a 30% likelihood of failure, compared to the subsequent model's 36% - meaning owners of the latter Mk V were 20% more likely to break down.

8 - Mercedes' current CLK less reliable than previous model

If you think it's astonishing that the Mercedes name should appear on this list with its high-priced CLK coupe-convertible, then check out Warranty Direct's Manufacturer Reliability Index and you'll see that the names you normally associate with quality, such as Porsche, Mercedes Benz, Jaguar, Audi and BMW are at the bottom of the list of manufacturers when ranked on reliability, and of the ten manufacturers on this list, only one is in the top half of the that ranking - Ford.

The statistics bear testimony to a significant decline in the reliability of the CLK model in the transition from the original CLK model (which was produced until 2002 and has a 28% failure rate) , and the subsequent and current model which has a likelihood of failure of 33% - roughly 18% less reliable.

9 - BMW's top selling 3 series became 11% less reliable from the E90 to E46

Rounding out a full cast of German auto manufacturers on the list, BMW 's iconic 3 Series has also had its share of woes. It's BMW's most important and top-selling model, accounting for approximately one third of all BMW automobiles made.

The fourth E46 generation of the 3 Series had a chance of failure of 27%, increasing to 30% for the fifth E90 series - that's 11% more likely to break down.

10 - Chrysler's current Jeep Grand Cherokee less reliable than last model

Ensuring a clean sweep for the Big Three American auto makers, the Jeep Grand Cherokee model produced from 1999 to 2005 had a reliability rating of 49% - it was replaced by the current model, which has a rating of 54% - that's more than 10% less reliable and has earned the Grand Cherokee the honour of being one of the most unreliable models currently on U.K. roads.

So what can we learn from these figures?

The figures are an indictment on the auto industry.

IMHO, the vehicles listed show either incompetence or intentional behavior on the part of the car companies.

We can believe that Ford Motor Company either knew its Ford Fiesta was significantly less reliable and frightfully more expensive to repair before it was produced ... or not!

We are led to believe by all automotive manufacturers that millions of miles of testing is done in harsh conditions every year, and that a huge percentage of an auto company's turnover is spent on continually testing its vehicles to ensure they are competitive.

In 2010, Ford's annual revenue was US$129 billion and General Motors was US$135 billion.

Are we expecting too much to want equally or more reliable cars as a result of this global patronage? Can't some testing be done before putting a car into global production to ensure it is not twice as expensive to repair as the last one? Or 50% less reliable?

We can believe that it was just an unfortunate glitch in the manufacturing process and that everything is fixed and it'll never happen again, or we can believe that it is a regular and ongoing occurrence. That ten of the world's largest and most respected auto makers have produced stinkers might also highlight a common problem - when you make cars lighter, and more fuel efficient and environmentally friendly, sometimes the reliability suffers.

Which makers are on the list is also telling.

There are no Japanese or Korean manufacturers amongst the top 10, yet Germany and America are represented in strength.

The two worst model changeovers in the list were both presided over Ford - Ford owned Jaguar from 1989 until it sold it to Tata in 2008.

Chrysler and Jaguar can at least claim some distance from the problems as both have been sold to new owners since their "lemons" appeared.

Indeed, am I justified in labeling the cars on this list as lemons?

I think so!

All these companies spend millions of dollars ensuring the world respects the technological expertise of their research departments, with massive well-organised PR departments that are characteristically the best in-house PR departments of any industry.

Yet the internal figures would have to contain ugly secrets.

I'm sure there would be far worse tales to tell if we could measure the reliability of cars in the sixties, seventies and eighties, but for new models to be 50% more likely to break down is unacceptable from the world's leading car makers.

No doubt the internal figures of all the manufacturers are different to Warranty Direct's figures - Warranty Direct's data sample represents an almost unfeasibly small percentage of global auto sales, and the ten manufacturers on the list between them account for a healthy chunk of global automotive sales and track the reliability of every vehicle produced.

Warranty Direct's sample may be small in comparison, but I am more than comfortable with it being large enough to accurately predict that there's a problem with the reliability of the automobiles we drive.

Given that all automobile dealerships are linked electronically, and have been for decades, the manufacturers would be monitoring the reliability of their cars very accurately in near real time, and would have been painfully aware within weeks of launch that their new car was less reliable then the old one.

Did they make it more palatable to their customers by reducing parts and labor costs until the reliability problems were contained? NO! They're still producing the same car in some instances.

Though all of the manufacturers on this list will be seen differently from this point, I think Ford's Fiestagate is the most telling - here's a top-selling global car series that was replaced by another that is 50% more likely to break down, and costs twice as much to repair when it does.

That's an unforgivable breach of trust with Ford's customers ... and given the degree of automotive sophistication we pay so handsomely for, it's inexcusable that cars should become less reliable.

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