The 29-year-old - who has been in trouble on several occasions throughout his career both on and off the pitch - had eight matches added to the four game suspension he had picked up already for being sent off in the final game of the season against champions Manchester City.
He was also fined ?75,000.
Barton, who also faces an internal enquiry by QPR into his behaviour, was shown a red card for elbowing Carlos Tevez and then kicked Sergio Aguero before appearing to attempt to headbutt opposing captain Vincent Kompany.
"There are rules of conduct that should be adhered to, and such behaviour tarnishes the image of football in this country, particularly as this match was the pinnacle of the domestic season and watched by millions around the globe," said the Commission chairman Maurice Armstrong.
The FA relased a statement saying that while Barton - who appeared personally with a barrister - had pleaded not guilty to the second charge the Commission had not found in his favour.
"This eight-match suspension is to run consecutively to the four-game suspension Barton was already given for his dismissal in the fixture, making a total of 12 matches," read the statement.
"Barton was charged by The FA with two counts of violent conduct in relation to the Queens Park Rangers game against Manchester City at the Etihad Stadium on Sunday 13 May 2012.
"Following Barton's dismissal in the 54th minute of the match, there followed two incidents involving Manchester City's Sergio Aguero and Vincent Kompany.
"As Barton had already been dismissed, both of these incidents fell outside the jurisdiction of the referee.
"Barton accepted the charge of violent conduct against Aguero but denied the second breach of violent conduct against Kompany. The independent Regulatory Commission, however, found this second charge proved."
Source: AFP
Source: AFP