The public protector also investigated claims that the Guptas had bribed state officials to win contracts at the state-owned electricity company, Eskom.

The Guptas said last year that there were no cases to answer and that they were in the process of clearing their name "in the face of unfounded media allegations".

What are the allegations against Zuma?

The inquiry will look into whether the former president played any role in the alleged offering of cabinet positions to politicians.

One politician, former ANC MP Vytjie Mentor, told the public protector that Mr Zuma was at the Guptas' Johannesburg home in 2010 when the Guptas offered her the post of public enterprises minister.

The family wanted her to cancel South African Airways route to India, she alleged.

The inquiry will also investigate whether Mr Zuma, and any other public officials, and their families, benefitted from the awarding of public contracts.

Mr Zuma's son, Duduzane, woked for the Guptas and has also been implicated in the allegations.

He denies that his relationship with the business family was improper.

What powers does the commission have?

The inquiry, known as the Zondo Commission, does not have power to prosecute but the evidence it collects can be used in any future prosecution.

It can compel people to give evidence and Mr Jonas and Ms Mentor are expected to be among the first witnesses to appear.

The commission could take up to two years to release its findings.