Germany on Tuesday demanded tougher rules on controlling diesel car pollution in Europe as it blamed auto manufacturers other than Volkswagen of using defeat devices to pass emission tests.

German Transport Minister Alexander Dobrindt told a meeting of his EU counterparts that a study of 50 diesel cars released in April exposed irregularities in pollution emission tests similar to those seen in the Volkswagen scandal.

The finger-pointing by Berlin comes after German authorities were deeply embarrassed by US revelations in September that national champion Volkswagen, the world's second biggest carmaker, illegally fitted special devices in 11 million diesel cars.

The defeat devices, which had been illegal in Europe since 2007, allowed Volkswagen vehicles to pass pollution tests they would have otherwise failed.

Dobrindt told his fellow ministers that an emissions probe found that 16 major car brands -- ranging from France's Renault to Italy's Fiat to Japan's Nissan -- also showed up irregularities, even though these did not involve the illegal technology used by VW.

"Some of the vehicles we tested seemed to show that the defeat devices installed were appropriate and the manufacturers could justify them and therefore they were a legal installation," Dobrindt said.

"In other cases however, there were doubts as to whether these devices were being correctly used and only being used in cases of protecting the engine against damage," he said.

As a result, Germany proposed that ministers accept a plan to toughen European rules on emission testing.

In a note prepared for the meeting, Germany said new rules should compel auto-makers to make an argument upfront for the presence of defeat devices in their cars.

Moreover, Germany recommended that the European Commission, the EU's executive arm, explore ways to widen auto testing and avoid dangers of conflict of interest.

Under current EU law, each car manufacturer wins the green light through a national regulator that allows it to sell the vehicles Europe-wide.

But critics have accused regulators of bias and for going too easy on their national auto-makers -- such as France with Renault or Britain with Land Rover.

EU industry commissioner Elzbieta Bienkowska downplayed the need for new rules, saying that European law is very clear on the use of defeat devices.

Enforcement of existing law should be key, she told the EU ministers.

Greens group MEP Claude Turmes said Germany's effort to "distract" from its own shortcomings had failed.

"National authorities have not been up to task," he said in a tweet.