After Mercedes had dominated the weather-affected Saturday race, BMW recorded a 1-2-3-4 on Sunday, with Marco Wittmann returning to the top of the standings.

Mortara had only lined up 18th for that race amid a disastrous qualifying for Audi - and while the Italian scythed his way through to sixth place by the chequered flag, he was disheartened by BMW's advantage.

Asked about Audi's qualifying trouble, Mortara told Motorsport.com: "To be honest with you, you had BMW being like four tenths faster than Mercedes. We were not actually far from Mercedes, but BMW was too strong in qualifying.

"It was just a joke. When it's like this, it becomes difficult to go racing.

"Today the difference was too big. Normally in the DTM we're not used to that much of a difference. I don't know what they did - I always have the impression that they're a little bit playing with us and probably today they pushed in full, and we had a true [picture], we saw what they can do."

Mortara left Moscow fourth in the standings, trailing Wittmann by 26 points, and the Italian believes BMW will be nearly impossible to catch if present form holds true.

"If they continue like this... [there] should be no championship," added the Italian.

"We're still going to fight and we're still going to try to make their lives hard - but we were one second off them in qualifying and we were pushing full. It's difficult for sure."

Green: Results speak for themselves

Having been relayed Mortara's comments, teammate and fellow title contender Jamie Green told Motorsport.com: "From the beginning of the year, obviously, we have this scenario of the different spec that they have.

"Unfortunately... the drivers are not involved in that, we don't have an input into those decisions, that's for other people to decide - I don't want to get drawn into that conversation.

Green's "different spec" comments was in reference to the controversial concessions made for the BMW M4 DTM at the beginning of the season.

The car's base weight was set at 1112.5kg compared to Mercedes-AMG C63's and Audi RS5's 1120kg, while BMW was also allowed to make its rear wing 5cm wider.