Eskom spokesman Khulani Qoma on Tuesday said he was told earlier this year by the utility's acting board chairman Zethembe Khoza that Public Enterprises Minister Lynne Brown had been "captured" by the Guptas.
Testifying during the parliamentary inquiry into corruption at state-owned companies, he told MPs this occurred after he recommended to Khoza that acting Eskom CEO Matshela Koko and its financial director Anoj Singh be suspended.
"Then he shocks me. He say this will be lucky if it succeeds. I asked him why and he said because Minister Brown is captured. He then explained that 'Minister Brown reports to the Guptas."
Qoma said Khoza had also told him that former Eskom board chairman Ben Ngubane had "come very close" to suspending Koko, but he "had been stopped in his tracks by Minister Brown".
Ngubane had received an anonymous letter with a list of allegations against Koko, and had called a board meeting to recommend Koko be suspended.
"Just moments before... Koko was called, "he (Khoza) snuck out of the room to 'make a call to a G brother'. I understood that to mean a Gupta brother.
"Khoza told me he snuck out and made a call to a G-brother and told him Koko was about to be suspended. They, in turn, made a call to the minister to instruct her to stop the suspension."
Responding to a question from the inquiry's evidence leader, Qoma said Brown "appears to be totally captured".
"She's in the water, she's completely submersed, and yet she says she's not wet," he said.
The inquiry into state capture is being conducted by the National Assembly's public enterprises committee, under the acting chairmanship of ANC MP Zukiswa Rantho.