Davids, who resigned from the unit last week, said the SIU should put the interests of the public above those of management, The Times reported on Wednesday.
“[The SIU is] significantly under-performing… the country expects more than what [it] is currently doing,” he said.
Former SIU boss Willie Hofmeyr fired Davids in 2010, reportedly citing incompatibility and loss of trust and confidence. Davids was reinstated in May this year.
He reportedly resigned after little more than a month after Vasantrai Soni was appointed head of the unit.
Davids denied that his decision to resign was because Soni had allegedly sidelined him, and said he had confidence in the SIU head’s leadership.
He said that on his return to the SIU he found that “the governance framework had not been respected”.
“Key positions were not being filled and the organisation was talking about operational strategy that was not being implemented,” Davids told the newspaper.