Debate surrounding the emissions of modern diesel engines has become a “non-issue”, according to Mercedes boss Dieter Zetsche.

“Emissions with modern diesels have become a non-issue because they are with gasoline [for equivalent emissions]. We don’t need to talk about ideological struggles, just the two topics I mentioned before,” said Zetsche, speaking to Autocar UK at the Paris motor show.

The two issues he referred to were regulatory requirements and the economic benefits. For as long as diesel is ‘legal’, is economically viable and can benefit buyers, it will have a place.

Zetsche said it’s these economic reasons why diesel has effectively died in the supermini segment. As petrol engines have become more efficient, the greater cost of a diesel engine has made the cars uneconomically viable because the efficiency advantages are no longer there.

“There might be a time when we see that in the C-segment [A-Class] but we don’t see it yet,” said Zetsche. “For bigger cars, there is a bigger difference and you don’t need to change diesel.”

Zetsche also said it is wrong to say Mercedes' diesel sales had “collapsed”. “It has declined but not as much as the rest of our competition and we have now seen stability for some time. But it’s lower than it was: that is also true,” he said.

Mercedes development boss Ola Kallenius, who will take over from Zetsche as head of the company in May next year, said the “NOx performance is technically solved” with diesel engines and cautioned that people “shouldn’t forget about CO2” and the role diesel can play in reducing CO2 emissions.

He said around half of Mercedes’ diesel customers are fleet buyers and they have taken a rational approach to the fuel and continue to support it as they “tend to stick to the facts”. Mercedes is also speaking to individual customers at the point of sale to deal with the perception problem around diesel.

“It’s not a losing battle,” he said.