World championship leader Nico Rosberg and his Mercedes team-mate Lewis Hamilton collided and retired in a sensational crash on the opening lap at Sunday's Spanish Grand Prix.

The two were scrapping for the lead and came together in a fashion that wrecked the team's hopes of another one-two triumph and revived the bitter memories of their collision in the 2014 Belgian Grand Prix.

"We have spoken to both drivers and it is not a clear cut decision - we have lost 43 points after lots of effort by the team in the last few difficult weeks," said Toto Wolff, the team chief.

Non-executive director Niki Lauda said: "It is stupid. We could have won this race... Lewis was too aggressive.

"I need to talk to them myself, listen to the explanations, and then we will see...."

Wolff said Lauda's comments were the instant emotional reaction of a former driver.