Deputy Chief Justice Raymond Zondo has responded to former president Jacob Zuma's claims that he should recuse himself from the state capture commission of inquiry on the basis that he believes Zondo is biased.

In a letter to the commission dated 28 September, the former president, via his legal team, said one of the reasons why Zuma wanted Zondo to recuse himself was that they had historical family relations.

But, in a statement released by commission secretary Professor Itumeleng Mosala on Thursday - a month after Zuma's letter - Zondo said that in the mid-1990s, while he was still practising as a private lawyer, he got into a relationship with a woman out of which a child was born.

"Unbeknown to anybody at the time, that woman's sister, Ms Thobeka Madiba, was, many years after that relationship had ended, to get married to Mr Jacob Zuma.

'No relationship'

"To my knowledge, Mr Zuma had no relationship with Ms Thobeka Madiba in the mid-1990s.

"That Mr Zuma happened to marry the sister of a woman with whom I had had a relationship that had ended so many years before that marriage, has never had any bearing on the execution of my judicial functions in the many matters involving Mr Zuma in which I have sat as a justice of the Constitutional Court since 2012, nor does it have any bearing on the execution of my duties as chairperson of the commission," Zondo said.

"Indeed, in none of the many matters involving Mr Zuma in which I have sat in the past, has Mr Zuma ever expressed any complaint or concern, nor has he ever brought an application for my recusal.

"I thought it is necessary to bring the above clarification, but I do not at this stage intend to address any of the other allegations made in Mr Zuma's attorney's letter as I will deal with them if and when Mr Zuma's application for my recusal is lodged."