Hamilton won the race, passing his team-mate on the final lap, but Rosberg broke his front wing and toured round to finish fourth. The gap in the drivers’ championship is down to 11 points.
The stewards announced they were putting Rosberg under investigation both for causing a collision and for driving a car for almost an entire lap with serious damage.
But Toto Wolff, the Mercedes boss, said the crash was “brainless”, and that Rosberg had a brake problem. Hamilton was booed on the podium by the Austrian fans but Rosberg appeared to be at fault for the crash.
A furious Wolff said: “Cars colliding seems a déjà vu. It’s absolutely not what we want. We are looking like a bunch of idiots and it’s disrespectful to 1,500 people who work their nuts off to prepare the cars and this is why it needs to end. We were marginal on brakes, if not to say completely over the brakes.
“We couldn’t tell the drivers so Nico had a brake by wire failure on to the last straight and defended very hard, then seeing both cars nearly colliding is upsetting.
“At the moment I don’t now what I will say to them. It could easily have been a double DNF.”
The accident comes just two months after the Mercedes pair collided in Spain on the first lap, taking each other out of the race.
Rosberg immediately blamed Hamilton, despite images showing he drove well wide and into his team-mate.
“I am absolutely gutted, it’s unbelievable,” Rosberg said. “I was sure to win the race and lost it on the last lap, that’s pretty intense.
Lewis Hamilton was booed on the podium after a last-lap collision with Mercedes team mate Nico Rosberg handed the triple Formula One world champion a dramatic first Austrian Grand Prix victory on Sunday.
Championship leader Rosberg, who had been in front with Hamilton in his slipstream, nursed his damaged car over the line for fourth place with his advantage cut to 11 points after nine of 21 rounds.