Eskom blocked whistle-blower Suzanne Daniels's return to work on Monday, and slapped her with fresh charges of "serious misconduct".
The decision came after the Commission for Conciliation, Mediation and Arbitration (CCMA) declared her previous suspension as "unfair".
The power utility said the new charges stem from a 2017 matter, which were not covered in the recent CCMA ruling.
Daniels is accused of "distributing confidential information, settlement of the McKinsey-Trillian matter and payments made to McKinsey and Trillian, as well as her involvement in the Optimum and Tegeta prepayments and guarantee issued by Eskom," the company said in a statement.
Eskom said "it would not be correct for Daniels to return to Eskom at this stage."
Daniels has been asked to give reasons why she should not be suspended.
"She has made representations and Eskom is considering these and will make a decision on whether or not to suspend her in the next couple of days," the utility said.
Approached for reaction to her latest tussle with Eskom, Daniels told Fin24 she would not be commenting at this stage.
The CCMA awarded her five months' pay as compensation and ordered that she be allowed to return to work on Monday.
The Eskom company secretary and head of Legal and Compliance, had lifted the lid on meetings she had with Ajay Gupta and his alleged attempt to exert influence at Eskom.
In November 2017, Daniels testified before the public enterprises committee's inquiry into state capture, detailing the influence of the Guptas and their business associates on the affairs of the state-owned enterprise.
Daniels was suspended in October 2017, after she ordered the law firm, Bowman Gilffillan, to issue letters of demand to McKinsey & Co and the Gupta-linked Trillian Capital Partners for payments the companies had allegedly received without valid contracts.
She was also probed over a team building exercise she organised at the luxury Kievits Kroon Country Estate in Pretoria.