The Hoops drew 0-0 with Reading this afternoon, ensuring that both clubs will drop into the Championship next season.
The midfielder, who is on loan at Marseille, tweeted: "Gutted for the club. Some good lads but not enough. Too many maggots.
"I can't believe QPR have just been relegated and [Jose] Boswinga was walking down the tunnel laughing! Embarrassing. Show some guts.
"Hope they can get a load out, if not they'll end up in a Wolves situation because trust me that Championship is a f*cking hard league!"
Barton, who was QPR's captain last season, joined the club from Newcastle United in 2011.