Johannesburg - Divisions within Cosatu are standing in the way of radical economic change, Numsa said in resolutions adopted by its national executive committee (NEC).
The Congress of SA Trade Unions (Cosatu) had previously committed itself to pursuing the ideals envisaged in the Freedom Charter, including strategic nationalisation, the National Union of Metalworkers of SA's (Numsa) said in releasing the resolutions on Sunday.
"It is precisely this programme of action that is being frustrated through divisions within the federation. The federation will be divided until the voices that call for nationalisation are completely silenced," it said.
Numsa, which is a Cosatu affiliate, adopted the resolutions at a special meeting last Sunday.
Cosatu general secretary Zwelinzima Vavi was placed on special leave last month after he admitted to having an affair with an employee. Vavi has claimed that forces are at work to discredit him.
Nine of the 19 Cosatu-affiliated unions have called for a special congress to discuss Vavi's reinstatement.
Numsa had brought an application in the high court in Johannesburg to have Vavi's suspension overturned. It was postponed after the court allowed an application to intervene by seven opposing unions.
In its resolutions, Numsa identified two camps within Cosatu - capitalists and socialists - which it said were fuelling internal divisions.
The capitalists sought to make workers tolerate white monopoly capitalist domination through the acceptance of some elements of the National Development Plan.
The socialists were encouraging workers to break this power dynamic through implementation of the Freedom Charter "as historically understood by the working class".
Numsa said it remained "unashamedly a socialist union".
"We are convinced that the recent attacks on Numsa by senior leaders of the alliance, in the context where Cosatu is in a state of paralysis, cannot be understood outside the ongoing conflict between the working class and the capitalist class both within and outside of the alliance," it said.
African National Congress secretary general Gwede Mantashe recently said a "cult of personalities" was behind Cosatu's problems.
"The concrete situation that we face today, in 2013, is that the ANC leadership is not just bureaucratised, it is also united in resisting the expropriation of imperialists," said Numsa.
It said Cosatu's position had become "ideologically incoherent" because some affiliates were in disagreement, and others were ignoring the debate about nationalisation.