The doctor in charge of obstetrics at a hospital where the disgraced gynaecologist Emil Shawky Gayed harmed hundreds of patients has warned the NSW health minister authorities have failed to take action to prevent other rogue doctors operating.

In an open letter sent to the Department of Health and health minister, Brad Hazzard, Dr Nigel Roberts wrote: “There remains an urgent need to address these issues to prevent a recurrence of poor outcomes. I remain very concerned that these systems issues are not being adequately addressed.”

As Guardian Australia revealed in numerous reports, Gayed needlessly removed women’s reproductive organs, left them with life-threatening post-surgical infections, and administered treatments that were not needed or were harmful, resulting in the death of one patient. His conduct triggered numerous inquiries and is now the subject of a police investigation. One of those inquiries was an independent investigation ordered by the NSW health department, led by the barrister Gail Furness SC.

Roberts, the director of obstetrics and gynaecology at Manning hospital in Taree, where Gayed worked for almost two decades, was asked in June 2018 to write a number of reports about Gayed’s conduct. He reviewed hundreds of case files from Gayed’s former patients, reassessed them, and continues to treat many of them.

Roberts drafted five reports highlighting concerns about Gayed’s management of patients, which he provided to the Furness investigation. The final Furness report was made public in February, stating that the cases of more than 50 women had been referred to the Health Care Complaints Commission for further investigation. Many of these cases were identified by Roberts.

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But Roberts said the health department’s reaction to the Furness report had been “slow, dismissive and buck-passing”. He also said the report had failed to make recommendations to address issues of fraud he identified.

“While Gayed worked in Taree, the Manning healthcare district had the highest rates of ablation and hysterectomy in New South Wales,” Roberts told Guardian Australia. Ablation is a procedure that surgically destroys the lining of the uterus and is most often performed to reduce menstrual flow in women experiencing excessive and painful bleeding.

“Gayed told women he needed to do the ablations to destroy fibroids,” Roberts said. “But the method he was using can’t destroy fibroids. Most of these women didn’t have fibroids. It’s fraud.

“He’s also having more complications as he’s doing more high-risk, unnecessary operations. You get paid way more for a hysterectomy or ablation than putting a Mirena [contraceptive implant] in.”

Gayed carried out a higher than normal rate of other procedures, such as a curette which is not generally needed in women under 35 but is a “fee-for-service procedure he could charge Medicare for”, according to Roberts.

At Roberts’ insistence, cases he identified were sent to the Independent Commission Against Corruption, which is investigating.

Roberts began working as the inaugural obstetrics and gynaecology director of the Manning Rural Referral hospital in Taree in April 2015, 15 years after Gayed started working there. By early 2016 Roberts had referred Gayed’s conduct to the Health Care Complaints Commission, and he suspended Gayed while this investigation took place. But Roberts did not know that there was a long history at Manning and other hospitals of complaints against Gayed, some of which had been reviewed by medical authorities.

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“When I started at the hospital, I very quickly had meetings with Gayed asking him to explain certain actions he was taking,” Roberts said. “Then I started going into the operating room to see what was happening. He threatened legal action against me and said he wasn’t able to talk to me without his lawyers present. I asked him to give me a copy of the letters he’d write to general practitioners so I could check whether patients actually needed the operations he was organising.

“I was accused of being racist, of picking on him and bullying him. When his case was heard by the medical tribunal in 2018, it was put to me that my concerns were motivated out of a ‘personality clash’.”

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The tribunal found Gayed guilty of misconduct and barred him from practising medicine for three years, based on the small number of cases identified by Roberts. Guardian Australia then uncovered a substantial history of Gayed harming patients spanning decades before this, sparking the subsequent investigations, including the Furness inquiry.

Roberts said he felt bitterly let down by what he perceives as a lack of support and action from the state’s health department. He still sees Gayed’s former patients on a weekly basis, with new victims coming forward all of the time.

The key issue was the health system’s inability to detect and prevent Gayed’s misconduct over decades of employment, Roberts said. Without widespread reform, including addressing fraudulent and unnecessary procedures, other doctors behaving unethically would be missed. In May Roberts resigned, frustrated by the lack of accountability. The health department encouraged him to stay and promised changes. Roberts agreed to stay but, after nothing changed, said he now felt compelled to speak out.

In his letter to the the department Roberts wrote:

“Failure to attend the fundamental flaws inherent in our health system that both enabled and encouraged the type of fraudulent behaviour that Emil Gayed has committed will mean that behaviour like Gayed’s will continue to be found in other doctors employed in Australia. Until we recognise that a fee-for-service model encourages over-servicing and fraudulent claims, and put in place preventative safe-guards, we will be facing these same issues again and again.”

A health department spokesman told Guardian Australia that “Dr Roberts showed compassion for the women affected by Dr Gayed’s treatment, supporting them during both physical and mental trauma”.

“The secretary, NSW Health has corresponded with Dr Roberts to personally thank him for the valuable role he played,” he said.

“In relation to allegations of fraud, these are criminal matters. As such the minister for health referred the matter to the NSW Police.”

But Roberts responded: “As Furness did not consider the issues of fraud, providing a copy of it to the police seems rather pointless from the point of the fraud issue”.

Guardian Australia is aware of five law firms assisting former Gayed patients. A Health Care Complaints Commission inquiry, an Icac inquiry and a police investigation are under way. Gayed, who is originally from Egypt and studied medicine in Cairo, did not respond to requests for comment.

Do you know more? melissa.davey@theguardian.com