The 29-year-old actor - who plays Finn Hudson in the musical comedy series - is said to have clashed with creator Ryan Murphy because he is unhappy about returning to filming almost immediately after finishing the 'Glee' tour and he also believes the actors should get a greater share of the profits from the show's spin-off albums.
A source told the New York Post newspaper: "Cory was the show's golden boy but has most recently been the most vocal member of the cast complaining. He feels they are being overworked. They were filming and toured without any time to recover.
"He's become a de facto leader complaining to Ryan Murphy [for the cast], who they feel should give them a bigger share of the show's success. But Ryan thinks Cory is causing trouble."
This isn't the first time the pair have clashed, with Cory previously admitted he only received $400 dollars from Glee's number one album.
He said: "I got 400 bucks from it going No. 1. But you know what, that's OK, because if I'm patient, and if this thing does really well, maybe I'll see another 400 bucks."
However, Corey's representative rep, "For the record, [this] is completely fabricated, I would imagine the result of lingering rumors from last month but not based in truth whatsoever. Cory is back on set and very happy to be there."