While stating he believes Barton has good ideas as Fleetwood Town manager, Onuoha admits he remains no fan due to calling him a playing teammate twice.
Onuoha said: “I never got on with Joey, ever, from academy times to this day. I have never had issues with him as a player, he played the game well, not the best in the world, but well. He had a lot of strong opinions, which lots of people disagreed with throughout his career.
"I ended any respect I had for him at City when he got me taken off at half-time in a game.
“It was against Aston Villa and he was having a nightmare. I kept seeing him going over to Stuart Pearce and then, when I got back to the dressing room at half-time, I was taken off.
"But he missed a pen and played like he had his shoelaces tied together.
“On the Monday he came over to apologise and I said from that point forward I couldn't care less what he had to say.
"We were playing together and that was it, nothing more."
Onuoha, speaking to Open All R's, the QPR Podcast, added: “We had some players at QPR who would play a great game on social media but they hated fans.
“Joey had a lot of power at QPR. He would say things, criticise, and there were no consequences. He would say someone was a bad egg but they were not."
Asked if Barton had wanted to get Neil Warnock sacked as QPR boss because of a feud that later erupted on Twitter, Onuoha said: “I have heard those rumours and they came from players.
"When we were at City together he tried to get someone to lose their job but he met with Richard Dunne (the former City captain) and Dunny wasn't having it."
Onuoha said Barton was also outspoken if he didn't like a manager's tactics. That included Harry Redknapp's ideas at QPR.
He added: “We were in Ireland pre-season. Harry wanted to play three at the back and two holders as well. But Joey was adamant that Harry was getting it wrong. As players you have to listen to your coach.
“We went a few days and he started to sabotage it. He wouldn't do it properly. Joey told everyone in front of Harry it wouldn't work and, come the start of the season, we played a different formation."