TWO-time world champion Casey Stoner has announced he will quit MotoGP at the end of the season for "family reasons".
The 26-year-old Australian, who has won 35 MotoGP races in his career and leads the current standings after winning two of the season's three events, made the announcement at a news conference ahead of Sunday's French Grand Prix.
"After a long period of thought and numerous discussions with my wife and family, I have decided to stop competing at the end of the season," Stoner said.
"After so many years taking part in this sport that I love, and with all the sacrifices that I have had to make, I no longer have the passion to continue and I think that it is best to stop."
Stoner, who also won the world title in 2007 with Ducati, became a father for the first time in February when his wife Adrianna gave birth to a baby daughter.
At the time he shrugged off suggestions that fatherhood would dampen his love of motorcycling.
"They say you slow down when you get married, but in my first year of marriage I won the title," Stoner said on the eve of the season.
"When I found out we were having a baby, I won it a second time. I don't think that's the case (that you slow down)."
Stoner joined the elite MotoGP class in 2006 with a satellite Honda team after working his way through the 125cc and 250cc ranks following his debut as a 125cc wildcard at Donington, England, in 2001.
His switch to Ducati in 2007 proved an inspired decision as he won the MotoGP season-opener in Qatar, followed by nine more victories that propelled him to the world title.
He moved to the factory Honda team last year and clinched his second title on home ground at Phillip Island, having already won nine races. Stoner closed the season with a 10th victory in Valencia.
"Casey just announced that 2012 will be his final year in the MotoGP Championship. Let's hope he has a fantastic year," said his Honda team on Twitter.