The X Factor singer was linked with a cameo appearance in the first live special of the ITV2 reality series.
However, Clark confirmed that he will not appear, and will unlikely sign up for future roles on the show due to other work commitments.
"TOWIE's a great programme and I wish them all the best of luck," he is quoted as saying in The Mirror.
"But I can't do the show because I've got commitments to the X Factor tour and I've got to be in rehearsals."
Speaking to Digital Spy, The Only Way is Essex stars Mario Falcone and Joey Essex recently threatened to leave if Clark joined the show full time.
Falcone told DS: "If he comes on Monday's live show, that's fine because it's all for charity, but if he comes on TOWIE as a main character, I'm leaving. We hate him. He's a douche-bag."
Responding to Falcone's comments, Clark added: "I can't believe these comments are coming from a man who cheated on his girlfriend.
"I've never met Mario in my life, so I find it very unprofessional and ungentlemanly for him to go around talking about people he hasn't even met.
"Anyone who cheats on his girlfriend that much isn't worth my time."
The Only Way Is Essex airs tonight (December 3) at 10pm on ITV2.