South African Revenue Service (Sars) Commissioner Edward Kieswetter has categorically ruled out the possibility of taking over as CEO of Eskom.

Two high-level government insiders have said Kieswetter was initially approached to consider taking over. However, Kieswetter told News24 on Friday he was out of the running. 

"I am not available. I am absolutely not available for any job [in government]," he said.

It is understood that top government officials who advocated for him to take charge at the ailing power utility argued that he was best placed for the job because he once worked there.

One high-ranking official said that Sars's successful turnaround under Kieswetter was another reason he made the list for the top job.

Kieswetter previously worked as a training manager for Eskom. He later became a top manager and moved to Eskom's Megawatt Park head office. He worked for the power utility for eight years and three months, before moving to FirstRand Bank.

Kieswetter told News24 on Friday that he had just over one year left at the helm of Sars and was ready to bow out after that. 

Eskom announced earlier on Friday that chief financial officer Calib Cassim had been appointed as interim CEO with immediate effect.

De Ruyter was initially set to leave Eskom at the end of March, but late on Tuesday night, it was announced that he was out with immediate effect. This followed an explosive interview in which De Ruyter said a "senior politician" was involved in corruption at Eskom.