Environmental campaigners have taken aim at famous German car brands like Porsche, Audi and BMW, criticising their high CO2 emissions as well as Germany's tax system they say promotes gas guzzlers.

A symbol of industrial might exported all over the world, Germany's sports vehicles, estate cars and 4x4s also enjoy huge domestic popularity due to what one campaigner derided as an "absurd" tax incentive scheme.

"Germany has the most absurd policy in the world of incentivising polluting cars," said Patrick Huth from pressure group Deutsche Umwelthilfe (German Environmental Aid or DUH).

Two-thirds of cars sold in Germany are registered to companies, although this percentage rises to 80 percent for the swankier models.

Companies can offset for tax purposes the entire price of the car and petrol without any fixed limit on carbon emissions, as there exists in other countries such as Ireland or France.

The more expensive the model, the greater the fiscal incentive for companies and in a country where cars are often seen as a status symbol, firms offer employees luxury vehicles to attract talent.

"Companies order heavy vehicles with high fuel consumption because image is more important to them than the fight against climate change," complained Sigrid Totz from NGO Greenpeace.

"This tax law ensures the German auto industry has a domestic market for its premium brands," added Totz.

The DUH group has calculated that the tax regime on cars owned by individuals is also one of the least strict in terms of carbon emissions in Europe.

And Huth criticised Germany's famously speed limit-free motorways, "the only case in the industrialised world" as an "incentive to buy souped-up vehicles."

Statistics appear to back up the campaigners' argument.

Germany routinely finds itself bottom of the class when it comes to the CO2 emissions of new cars sold in the country.

Over the first seven months of 2012, cars sold in Denmark and Portugal spewed out on average less than 120 grammes of CO2 per kilometre travelled while in Germany, this was over 140 grammes, according to manufacturers' data.

--- Suckers for horsepower ---

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Nevertheless, the top companies are striving to improve the situation, said Matthias Wissmann, from the VDA association which represents the Germany auto industry.

"Since 2006, the German brands have cut their average (fuel) consumption by 20 percent" thanks mainly to billions of euros invested in improving motor efficiency, Wissmann said.

And Ferdinand Dudenhoeffer, an expert from the CAR-Centre for Automotive Research at the University of Duisburg-Essen, said environmentalists should not necessarily point the finger at the top brands.

"Premium German carmakers have made more progress than lower range manufacturers," he told AFP, adding that many top-of-the-range vehicles have similar emissions to less modern and less expensive cars.

German manufacturers "have invested enormously in technology and have no problem respecting the CO2 emission limits in Europe," he added.

Consumers in Germany do however tend to be suckers for horsepower, with a trend for ever bigger engines, a study conducted by Dudenhoeffer in August showed.

In the first seven months of 2012, the average horsepower of the engines of new cars sold in Germany stood at 138 hp, up from a previous record of 135 hp seen in 2011 and 130 hp in 2010.

Nevertheless, "more horsepower does not automatically translate into higher fuel consumption," given new generation fuel-saving technology, Dudenhoeffer wrote as a conclusion to that study.

The expert did acknowledge that Germany had a lot of catching up to do in the area of hybrid vehicles, where motors are driven by a combination of fuel and electricity.

Over the first 10 months of the year, Japanese giant Toyota seized 75 percent of this market in Germany, ahead of French group PSA (Peugeot-Citroen), itself ahead of German manufacturers.

For Huth, this too can be put down to the "near-absence of tax incentives" to develop greener cars in Germany.