The National Anti-Corruption Commission (NACC) says that six public officials will now be investigated over their part in the illegal welfare debt scheme.

Its original decision prompted more than 900 complaints.

The backflip follows a review by NACC Inspector Gail Furness last year. It found that commissioner Paul Brereton did not properly deal with a conflict of interest which should have required him to excuse himself from the process.

Brereton declared he had a “close association” with one of the people referred to the NACC by the royal commission and delegated decision-making to one of his deputies.

But Furness said Brereton should have removed himself entirely.

The NACC said yesterday an independent review of the matter by former judge Geoffrey Nettle had recommended the decision be reversed.

The anti-corruption body said a new probe will seek to find whether or not any of the six people referred to it had been involved in corrupt conduct.

“Consistent with its usual practice, the commission does not publish reasons for commencing an investigation, as doing so may prejudice the investigations, disclose information which the commission is required by law to keep confidential, compromise investigative pathways and/or unfairly impact reputations and rights of individuals to impartial adjudication.

“The commission is now making arrangements to ensure the impartial and fair investigation of the referrals, as it did with the appointment of Mr Nettle as independent reconsideration delegate.”

The NACC says Brereton and those deputy commissioners who were involved in the original decision not to examine the referrals will not be part of the investigation.

Robodebt raised $1.73 billion in unlawful debts against more than 400,000 people during its four-and-a-half years of operation, and the royal commission found it had led to three suicides, and likely many more.

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