Public Enterprises Minister Pravin Gordhan is demanding an apology from the ANC and the retraction of a statement the party issued on Wednesday.
According to the ANC's statement, Gordhan and Senzo Mchunu, both allies of President Cyril Ramaphosa, launched attacks on black professionals.
The party said it distanced itself from Gordhan and Mchunu and that it would seek to engage with them.
But in a letter addressed to Ace Magashule on Thursday, Gordhan says he rejects the ANC's assertions and that he finds them "extremely offensive".
"I want to state emphatically that I have not made any statements diminishing the status of black engineers," Gordhan's letter reads.
He adds: "It would appear that some individuals at Luthuli House give more credence to the orchestrated utterances of individuals like Matshela Koko who has done so much damage at Eskom. Accordingly, I must insist on a retraction and an apology from the ANC spokesperson."
The ANC's communication was issued under the names of Zizi Kodwa and Dakota Legoete, the party's acting spokespersons.
Another spokesperson, who did not want to be named, told News24 that Gordhan and Mchunu blamed "black professionals" for the dire situation that the parastatal was in.
Neither Kodwa nor Legoete answered their phones when called for comment.