The midfielder was docked six weeks' wages and warned that any further misconduct could see him sacked, after a meltdown against Manchester City on the final day of last season.
Barton was sent off for striking Carlos Tevez and committed two further acts of violent conduct on his way off the pitch, and has been banned for the first 12 matches of the 2012/13 campaign.
A club statement said: "QPR FC can confirm Joey Barton has been fined six weeks’ wages and will no longer be club captain.
"The 29 year-old midfielder will also be absent from the club’s pre-season tour of Asia in July.
"If Barton seriously breaches the Club’s disciplinary procedures again, the Club reserves the right to terminate his contract."
In a statement on the QPR website Barton, who is holidaying in North Africa, said: "My behaviour was wrong and I accept the punishment that has been imposed upon me as a result.
"I apologise to the Manager, my team-mates and of course the QPR fans for my actions. I also apologise to the Manchester City players, staff and supporters."
Although the club said Barton would make no further comment, he immediately said on Twitter: "I was reckless and deserved every punishment I received. Money comes and goes, it's not important to me. Losing the captaincy and missing 12 games, is what really hurts. I was stupid and that's what happens when you do dumb things. I am confident I'll bounce back. Cannot wait."
Barton's club fine will cost him around £480,000 - he is paid £80,000 a week - plus another £75,000 already levied by the FA.