The 26-year-old will observe the remainder of the club's tormented season from afar after being told to stay away from the training ground in the wake of Sunday's 3-0 Barclays Premier League defeat at Liverpool.
Barton was sent off for a rash challenge on Xabi Alonso which saw him banned for the last three games of the campaign, and is then understood to have become embroiled in a furious row with manager Alan Shearer in the dressing room afterwards.
The club have suspended him until further notice to write a new chapter in the troubled player's chequered career less than two years after then Magpies boss Sam Allardyce handed him a lifeline.
Moncur, the last Newcastle captain to lift a trophy, said: "Big Sam signed him and at the time, he thought he could do something with Joey Barton. But often when a manager thinks he can do that, it proves not to be the case.
"I'm just disappointed because last season, he started to look a decent player. The sad thing is, he will be hard to change."