Former public protector Thuli Madonsela has warned that suggestions for the extension of the scope of the commission of inquiry into state capture pose a risk for the investigation to be side-tracked.

This comes after Madonsela's successor Busisiwe Mkhwebane this week called for the extension of the terms of reference of the commission to be headed by Deputy Chief Justice Raymond Zondo.

Mkhwebane said this would ensure that "no stone is left unturned in so far as the allegations of state capture are concerned". Her comments did not go down well with Madonsela, who published the State of Capture report, the SACP and the Ahmed Kathrada Foundation.

Madonsela told Sowetan yesterday that although "it would be improper" for her to comment against her successor, the "vision" behind her report's remedial action was that the commission would conclude the probe she started.

"The investigation [state capture inquiry] is solely to conclude the investigation started by the public protector, it has no other purpose other than that," Madonsela said.

She said her report stipulated that the commission appointed had to conclude the investigation.

"During the investigation, the deputy chief justice may be alerted of other forms of wrongdoing that is similar to what he's investigating ... it will be easy to integrate, that's normal in any commission of inquiry," Madonsela said.

"If you are investigating who stole Mr Nkambule's goats, in the process of investigating you find that actually somebody else stole his sheep, you're not going to [be] side-tracked and now start investigating who stole his sheep."

President Jacob Zuma told the National Assembly in November that the inquiry would investigate any corruption raised by citizens.

Madonsela said she found it "strange" that Zuma would suggest that the scope of the inquiry be expanded.

The Ahmed Kathrada Foundation echoed Madonsela's view and called for Zuma to use the powers at his disposal to set up other commissions for his other concerns on state capture.