A culture of conflict and mistrust inside a Sydney oncology department enabled a doctor to prescribe off-protocol chemotherapy to patients for a decade, a report has found.

Between 2006 and 2015, medical oncologist Dr John Grygiel prescribed a flat dose of 100 mg carboplatin to 129 mostly head and neck cancer patients at St Vincent’s Hospital, a practice that was off-protocol.

As early as 2005, staff had questioned the doctor about this practice.

However the hospital only acted in 2015, when a radiation oncologist raised the alarm after noting an increased number of recurrences in head and neck patients. Two inquiries, internal and external, were then undertaken.

These details are documented in a report by a parliamentary committee released last week, which finds it “not credible” that senior staff did not know the flat-dosing was happening and is “not able to discount the possibility of a cover-up” by St Vincent’s.

The hospital’s culture was the “primary contributor” to the failures in its response finds the report, which draws heavily on a 2016 external inquiry ordered by the NSW Ministry of Health.

That investigation concluded that inadequate clinical governance, poor incident notification and a “culture of conflict and mistrust within the oncology department” contributed to Dr Grygiel’s prescribing practices “enduring for a decade”.

The hospital’s cancer services stream was riddled with “tensions, unresolved grievances and conflicts” which left it ill equipped to manage the issue in a timely or patient-focused way.

Junior pharmacists, junior doctors and oncology nurses had raised concerns with the oncologist, the 2016 report found.

“However, each time clinicians accepted Dr Grygiel’s explanation, and so did not act on the flat-dosing as a clinical ‘incident’, even though the practice was outside protocol and no evidence supporting it was provided”.

In 2012 an entry about the doctor and flat-dosing was logged in the incident management system but an incident report was never completed.

The hospital only informed the Ministry of Health in February 2016 after it received the external inquiry report and was preparing to inform patients, shortly before the scandal became public, the committee found.

Since then, the hospital has put in place new systems for staffing, incident management, open disclosure, electronic prescribing and is addressing cultural change.