FRANKFURT — BMW, responding on Sunday 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, can hardly afford another blow to their reputations. They were already under fire after several government studies showed that diesel cars, once promoted as environmentally 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.