The ABC ombudsman on Tuesday found two episodes of the Four Corners program led by a bikie-turned-journalist had breached editorial standards.
Mahmood Fazal was sacked in May and has denied any wrongdoing after questions were raised regarding the anonymous sources used in the Cocaine Nation and Meth Highway episodes aired during 2023 and 2024.
Both were removed by the ABC due to accuracy concerns.
ABC chairman Kim Williams elevated the allegations to ombudsman Fiona Cameron who found the national broadcaster had failed to meet its own editorial standards for accuracy, fair and honest dealing, and independence and integrity.
Audiences were given a misleading impression of who key contributors were, according to the report from Ms Cameron.
In both episodes, a masked figure who purportedly dealt cocaine to Sydney's elite was featured.
Media Watch later reported Sydney-based rapper Charissa Habkouk played the role as a favour to Fazal.
Ms Cameron confirmed this was "materially misleading" to the audience recommended a full investigation in the use of anonymous and confidential sources.
The broadcaster has since pulled another three stories by Fazal for Four Corners and the Background Briefing podcast over similar concerns regarding anonymous interviewees.
"The breaches were the result of a combination of factors," Ms Cameron said, noting management's failure to interrogate and a culture that favoured limiting knowledge about sources.
"The cumulative effect of these failings undermined confidence in the integrity of the programs and caused the ABC to fall short of its editorial obligations."
The Four Corners team should also set clear expectations about fact-checking and to ensure junior reporters receive greater support from management when making high-risk programs, the review found.
The ABC accepted all seven recommendations and has begun to implement them.
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