Johannesburg - Cosatu president Sidumo Dlamini on Monday urged members not to make "wild accusations" about the trade union federation's general secretary Zwelinzima Vavi, SABC radio reported.
Vavi faced an internal grievance hearing on Monday following a complaint of sexual harassment by a colleague.
"I'm not going to respond to that question... [of] political conspiracies," Dlamini told SAfm in an interview.
"We have to be careful not to flout internal procedures by making wild accusations, and we must respect the processes that are put in place.
"I want to call upon everybody in the federation to respect internal processes without making these allegations. Everybody is presumed innocent until proven guilty."
He confirmed that a "grievance matter of sexual harassment" would be heard against Vavi on Monday.
"I do not want to discuss it publicly," said Dlamini.
"It's an internal process.... I'm not going to talk about the details."
On Saturday, Vavi released documents to the media, in which he claimed to have been a victim of extortion by a woman and her husband. Vavi released an internal complaint by the woman in which she accused him of rape.
Vavi admitted to having an extramarital affair with her, and said she had later tried to extort R2m from him. He denied raping her, and said the sex was consensual.
The woman wrote an open letter to the Sunday Times in which she described how Vavi offered her a job at the Congress of SA Trade Unions without going through the correct processes.
She described how he "grabbed and kissed her" while she worked there, but she did not go into more details about the alleged incident.
The woman's husband told The New Age she would attend the hearing on Monday.
"She [my wife] is caught between a rock and a hard place. She is seeking legal advice," the husband was quoted as saying.
"We will be waiting for the outcome of the hearing."