Football’s bad-boy grabbed his opponent around the neck and wrestled him to the ground during a 'friendly'.
The pair were separated by players and staff but Barton continued the row by jabbing his finger towards Istres striker Guy-Roland Niangbo and his team-mates.
QPR midfielder Barton is still serving a 12-match domestic ban for his madness at Manchester City on the final day of last season.
Barton later admitted he cannot help himself when he crosses the white line.
He posted on Twitter: "I still haven't grasped the meaning of the word 'friendly'."