Moto2 World Championship leader Marc Marquez will have to start Sunday's Australian Grand Prix from the back of the grid for causing a big accident in Friday morning practice.

Marquez, seeking to make up for time lost in an earlier fall, continued at high speed after the chequered flag - and slammed into the back of a slower-moving Ratthapark Wilairot through turn two.

The incident was examined by Race Direction, who reprimanded M?rquez for 'riding in an irresponsible manner' with a one-minute penalty to be added to his best lap time in Saturday's qualifying session.

M?rquez's team lodged an appeal against the decision, following which FIM stewards confirmed the decision of Race Direction.

Wilairot was airlifted to hospital for precautionary medical checks, while Marquez walked away from the incident with minor injuries and was able to take part in the afternoon session, which he finished in 17th place.

"When the session was about to finish I went out to do a lap and check that everything was fine after the [first] crash." explained Marquez. "When the session was over and after the finish line, I was finishing the lap to go back to the garage when in the third corner - which is very fast - I saw a rider.

"I was not going too fast, but the track is very fast and in that corner, which is normally taken in fifth, I was maybe on fourth. When the other rider got out of the way I saw that Wilairot was behind him and I was not able to brake.

"I hope he is fine, because it was a hard crash and I was not seriously injured, so I wish him the best."

Repsol Suter rider Marquez took the title lead by one point from Stefan Bradl at the previous Japanese round. Kalex rider Bradl was fastest on combined Friday practice times at Phillip Island.