Senior staff at Sydney's high-profile Northside Clinic were warned about the "inappropriate" and "dangerous" behaviour of its star psychiatrist, Dr Ong Ming Tan, years before he was stood aside for indecently assaulting patients.

Key points: Ong Ming Tan was convicted of indecent assault of four of his patients

Ong Ming Tan was convicted of indecent assault of four of his patients Senior staff at the clinic raised concerns about Tan's behaviour as far back as 2006

Senior staff at the clinic raised concerns about Tan's behaviour as far back as 2006 Northside Clinic says there was nothing different it could have done to prevent Tan's abuse of patients

The Northside Group last month paid a settlement to nine former patients who sued the clinic for negligence after being groomed, abused and in some cases drugged by Tan between 2009 and 2011.

Tan was released from jail in March after serving two years for the indecent assault of four of those young women, who he was treating for eating disorders at Northside Clinic and the Metta Clinic, both on Sydney's North Shore.

Several of Tan's victims had histories of sexual abuse and have told 7.30 he convinced them he was exposing them to their trauma by asking inappropriate questions, setting sexual tasks, kissing and touching them inappropriately.

Among the victims was Bonnie Foulds, a 23-year-old teaching student with a history of suicide attempts, who took her own life in January 2012 after being weaned off a dangerous combination of drugs prescribed by Tan.

Ms Foulds' parents told 7.30 after Tan was stood aside, and weeks before her death, she disclosed that his sessions had involved her sitting on his lap.

7.30 has obtained minutes of a meeting and patient records that show senior Northside Clinic staff had raised concerns at that time that Tan had put Bonnie Foulds on eight psychotropic drugs at once in dangerously high doses.

Bonnie Foulds' family complained to the Health Care Complaints Commission about her treatment but in its response dated August, 19 2013, the commission said it "did not identify any issues that would require a formal investigation" into Northside Clinic.

Bonnie Foulds told her parents about inappropriate sessions with Ong Ming Tan shortly before her death in 2012. ( Supplied )

Northside Group is owned by Ramsay Health Care, Australia's largest private hospital operator and a giant in the global private health care industry.

7.30 has obtained sworn police statements from senior Northside Clinic staff, which detail a series of complaints and concerns about Tan's inappropriate and dangerous behaviour.

In one of the statements, a Northside Clinic medical director said she had concerns as early as 2006 that Tan was "prescribing inappropriate dosages and combinations of medications in prescribing patterns which were possibly dangerous".

"I and other members of the treatment team raised these concerns with Dr Tan," the statement said.

Patients told 7.30 they were groomed and touched inappropriately by Tan in night-time sessions which could last for up to two hours in his darkened office with the door locked.

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Tan turned the young women against their families, threatened to become their legal guardians if they spoke about his sessions and in some cases prescribed extreme doses of sedating drugs.

"The over-prescribing of medication was deliberate, was done so that his patients presented in a manner that he could actually prey on them and manipulate them," their lawyer, Sally Gleeson said.

"For days on end, they couldn't remember what had occurred, they couldn't remember leaving the room, they couldn't remember having breakfast or dinner, they couldn't remember the sessions that he had with them."

Staff raised 'concerns' in 2009

Northside Group CEO, Anne Mortimer, says there's nothing Northside Clinic could have done differently.

In her police statement, the medical director said she "continued to be concerned about Dr Tan's professional competence" in 2009, when she "met with Dr Tan, the CEO and other clinicians ... following concerns expressed by [fellow clinicians] about possible boundary violations".

"I had wondered if he understood the concept of boundary violation," the statement reads.

"I was reassured by management that 'more governance' would be 'put around Dr Tan'."

But in an interview with 7.30, Northside Group chief executive Anne Mortimer denied the meeting had taken place.

"Staff did not raise boundary violations with me in 2009," she said.

"The only time that staff raised boundary violations against Dr Tan was in 2011, when we acted."

Exterior of the Northside Clinic in Greenwich

In 2011, six months before Tan's patients went to police, a female psychologist on the Eating Disorders Unit complained about him to Northside Clinic's Bullying and Harassment Officer after catching him going through her photos on her phone without her permission.

In her sworn police statement, the psychologist said: "Tan insisted on kissing me on the cheek and hugging me when we met."

"During this time Dr Tan also started to say words such as 'I love you', 'your brain completes my brain', 'I think we were married in a previous life'," she said.

"When I reported to him that a patient had lost weight, he would say, 'Don't worry, I'll spank her'."

"On numerous occasions, I asked him not to use that word because I found it to be of a sexual nature and I felt it was inappropriate."

"I reported these comments."

A nurse also saw photographs of a patient on Tan's phone which she described in her police statement as "sexually suggestive".

'There's nothing we could have done differently'

Northside CEO Anne Mortimer told 7.30 there had been "no indications that [Tan] was acting in any way shape or form in an irregular way."

"We have no reporting or oversight problem" she said.

"I don't think there's anything we could have done differently.

"He was an extremely deceptive predator. He groomed all of his patients and he groomed the organisation."

Ms Mortimer said that as a result of the Tan case, Northside Clinic had installed windows so that patients could be sighted during private sessions and educated patients about "what to expect from their health professionals".

Ong Ming Tan has been suspended from practicing medicine and is being prosecuted by the Health Care Complaints Commission for professional misconduct.

Tan is awaiting a ruling from the New South Wales Civil and Administrative Tribunal on whether he will be permanently deregulated.