Cosatu secretary general Zwelinzima Vavi said on Sunday that he is not resigning from the federation.

"This is a deliberate act of defiance on my part, even if in the end it turns out to be symbolic," he told reporters at a briefing in Johannesburg.

"It sends a message to workers that we must refuse to hand the organisation over on a platter, and must not only walk away when all alternatives to rescue it have been exhausted."

Cosatu belonged to all its members, and not any faction or clique, he said.

Vavi called a media conference to make "an important announcement," with many speculating that the beleaguered unionist would leave the federation.

On March 5, the CEC announced that a forensic report into alleged impropriety in the sale of Cosatu's old head office and purchase of a new one implicated Vavi.

The report, by auditing firm Sizwe Ntsaluba Gobodo, which was handed to the CEC, showed that the auditors had not been able to meet Vavi despite their attempts to do so, the federation said then.

There were allegations that Vavi's stepdaughter was involved in one of the companies that worked on the head office transaction.

Vavi did not attend the CEC meeting on March 2, and instead attended a case in the High Court in Pretoria against mine company Aurora by its workers.

The embattled trade union federation has been dealing with its unions supporting either Vavi or Cosatu president Sdumo Dlamini.

Members of the National Union of Metalworkers filled the conference room and sang revolutionary songs at Cosatu headquarters.

Dressed in Numsa T-shirts, they sang songs supporting Vavi.