An independent review into a disgraced gynaecologist who performed needless and irreversible surgeries on dozens of women throughout New South Wales has been extended by one month.

In June the NSW government appointed the high-profile barrister Gail Furness SC to conduct an independent inquiry into Emil Gayed and the five public hospitals throughout the state where he worked.

It followed a Guardian Australia investigation that revealed Gayed operated on his patients without their informed consent. One of his patients died following inadequate care.

A separate Health Care Complaints Commission investigation found he removed the healthy fallopian tube of one woman and needlessly performed a hysterectomy on another.

While the scope of the Furness investigation is limited to NSW, Guardian Australia revealed complaints were made about Gayed more than two decades ago while he worked in Canberra.

Furness has been ordered to examine the quality of care and safety of patients treated by Gayed, the management of any complaints, adverse events or performance issues relating to Gayed, and subsequent action taken by the local health districts who employed him.

Furness was asked to report back to NSW Health by 30 September but a NSW Health spokeswoman said on Tuesday afternoon the deadline had been extended to 31 October.

“This is the same date on which Ms Furness is required to return her report on the actions of the NSW Medical Council (formerly the NSW Medical Board) in the approach to the management of complaints about Dr Gayed in concert with its co‐regulator, the NSW Health Care Complaints Commission,” the spokeswoman said.

Former patients of Gayed’s with concerns about their treatment are still being encouraged to come forward. Gayed worked at Grafton base hospital, Cooma hospital, Kempsey district hospital, Manning base hospital and Mona Vale hospital.

Those who wish to make a submission to the inquiry can email gayedreview@health.nsw.gov.au.