He said the union federation needs to focus on its principles.
"Once you close your eyes to those fundamental principles you are going to see the battles that are running now," he told Police and Prisons Civil Rights Union (Popcru) members at their second national political school in Benoni.
"Those battles are a function of many things."
Mantashe said one of those things was the development of personalities in the trade union federation.
"When you begin to worship individuals then you are going to kill the thing [Cosatu]."
Cosatu has been divided following allegations of rape against its general secretary Zwelinzima Vavi.
Vavi was put on special leave pending outcomes of a disciplinary hearing into an affair he had with a junior employee, but he vowed to challenge his suspension.
Cosatu affiliates such as the National Union of Metalworkers of SA and the Food and Allied Workers Union have backed Vavi.
The unions have called for Cosatu president Sidumo Dlamini to be removed from his position after he made comments saying damage had been done to Cosatu. They also claim the special central executive committee meeting which suspended Vavi was not constituted properly.
Numsa, Cosatu's biggest affiliate, said it had lost faith in Dlamini and that he was not representing all Cosatu affiliates.
Mantashe said Cosatu needed to appreciate the fundamental principles and focus on its responsibility to workers.
"You gave power to general secretaries and killed worker control," he said.
"Once you do that you tamper with the content and nature of the trade [union] movement," he said.
- Sapa, Fin24