Renault chief Carlos Ghosn said Friday his company, which is under pressure over failed emissions tests, had not committed any "deception", amid sector-wide questions sparked by a pollution cheating scandal at Germany's Volkswagen.
Ghosn, speaking on France's RTL radio, also called for new rules on emissions norms to avoid any "confusion", after some Renault vehicles' emissions were found to differ between laboratory and real driving conditions.
"There isn't any deception," he said. "Are there deceptive installations, software? The answer is no."
The chief executive rejected any comparisons with Volkswagen, which has admitted fitting around 11 million vehicles with software which turned on pollution controls only when it undergoing emissions testing.
"Do we meet the regulations?" asked Ghosh. "No car can be certified unless it meets the regulations, all Renault cars have been certified, they meet the norms."
However certification tests are made in laboratories under controlled conditions which have little resemblance to real road driving practices.
The tests ordered by the French government after the Volkswagen scandal broke were under road conditions.
Several Renault vehicles plus non-French cars whose manufacturers have not been publicly disclosed were found to be polluting more than regulations allowed when driven on the road.
No evidence of cheating software was found on the Renault cars.
"It is clear that when you use a car in a manner in which is completely different from conditions under which the certification takes place that the emissions are different and often superior," said Ghosn.
"All carmakers have higher emissions" in road conditions than laboratory tests.
"The question is by how much -- five times, seven times, 10 times, 15 times, 20 times?"
He said there were no rules on what is acceptable, calling for clear guidelines so consumers don't feel confused.
The current emissions testing rules came in for criticism as being obsolete during the Volkswagen affair. The EU is discussing new testing rules that reflect much more closely normal daily driving conditions which are expected to be adopted next year.