Koko told TimeLIVE on Friday he had “no reason to doubt Dr Ngubane's” evidence.
Regarding the sexual escapade claim made by Tsotsi against him, Koko said this was “fabricated”.
“It was rubbish. That is why he failed to produce the video. He was just being a tsotsi from Zola,” said Koko.
Ngubane told the inquiry that in a meeting on March 11 2015, Tsotsi admitted he had failed to produce the report implicating the executives in the misdemeanours he had alleged in the previous meeting, despite pressure from board members.
“The board said: 'Give us the report'. He did not give us the report. The board took the decision to approach the shareholder (then public enterprises minister Lynne Brown). At that point the board had started to doubt Mr Tsotsi’s credibility.”
The board later that month forced Tsotsi to resign from the board.
Tsotsi's version at the inquiry was that Brown had instructed the board to remove him because the two of them did not get along.
Of the four executives suspended by the board without reason, three settled with Eskom for R6m each and chose to leave while Koko was reinstated.