BOULOGNE-BILLANCOURT, France - Renault (IW 1000/82) on Monday promised to come up with a "technical plan" over coming weeks to bring down harmful emissions of its vehicles.

On Thursday, a French government-appointed commission said that Renault's diesel cars failed pollution tests and investigators raided its facilities, raising fears the French carmaker could be caught up in an emissions scandal similar to the one engulfing Volkswagen, which has admitted to using cheating software to fool tests.

The commission said test results on French and foreign vehicles had found carbon dioxide and nitrogen dioxide emissions in Renault cars to be too high, as were those of several non-French.

"We are working on a technical plan which should allow us to cut emissions," Renault sales director Thierry Koskas said during a presentation on the group's 2015 sales performance.

"The plan is being elaborated by our engineering team and will be presented in coming weeks," he added.

Unit sales grew 3.3% from 2014 to 2.8 million units worldwide.

"Renault did not cheat," Koskas said, referring to questions raised last week over how emissions levels could be so different between test conditions and real conditions on the road.

"I want to restate this very firmly," he said. "We are not using any software or other [fraudulent] methods."

"In test conditions, we respect emissions norms," he said.

"But when we are no longer in test conditions, there is indeed a difference between real conditions and control conditions; that is a fact," said.

He gave no details of what the "technical plan" may entail, but said that Renault would be meeting with the government-appointed commission later on Monday for "technical discussions."

Shares in Renault and other car companies skidded last week amid fears that the emissions scandal engulfing Volkswagen may be spreading sector-wide.

Renault stocks slumped by more than 20% during Thursday's session after unions reported that anti-fraud investigators had raided several of the company's sites, possibly looking for emissions cheating software on diesel engines, before closing around 10% lower. On Friday, they lost another 3.4%.

Copyright Agence France-Presse, 2016