FRANKFURT (NYTIMES) - BMW, responding on Sunday (July 23) to claims it formed a cartel with Daimler and Volkswagen to hold down the prices of crucial technology, denied that the German carmakers had agreed among themselves to install emissions equipment that was inadequate to do the job.

The statement by BMW was the first attempt at damage control by the carmakers since the European Commission said on Saturday that it was investigating accusations of illegal collusion among them.

The German carmakers, who dominate the global market for luxury cars, were under fire after several government studies showed that diesel cars, once promoted as environment-friendly, frequently pollute much more than advertised.

Adding to the pressure, the accusations against the automakers showed signs on Sunday of becoming an issue in coming national elections. Chancellor Angela Merkel and her transport minister, Alexander Dobrindt, faced increasing criticism that they had been overly accommodating to the carmakers and had enabled wrongdoing by them.

Martin Schulz, chancellor candidate for the left-leaning Social Democrats, said that if the allegations proved true, "it would be a gigantic fraud against customers", according to news reports.

Motor vehicles are Germany's biggest export, and Volkswagen, Daimler and BMW are among Germany's largest employers.

In its statement on Sunday, BMW said that discussions with the other carmakers had been about how to ensure that customers would be able to buy refills of a chemical needed for pollution equipment in diesel vehicles. The chemical, a urea solution sold commercially as AdBlue, is sprayed into the exhaust to neutralise harmful nitrogen oxides.

"From a BMW Group perspective, the objective of discussions with other manufacturers concerning AdBlue tanks was the installation of the required tanking infrastructure in Europe," BMW said.

German magazine Der Spiegel reported on Friday that the carmakers agreed in 2006 to limit the size of the tanks used to hold AdBlue to save space in the car that could be used for sound systems or other features. Volkswagen has admitted that its vehicles were programmed to ration doses of AdBlue, leading to excess emissions. Der Spiegel said it had seen documents that were part of an antitrust investigation.