The public service broadcaster engaged in a "serious breach" of media regulations by omitting to mention that the voice of a film about the Gaza situation was the offspring of a Hamas representative, according to UK media regulator Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has determined that the programme was "substantially inaccurate".
The BBC's director general had already issued an apology, noting there had been "a significant failing in relation to factual correctness".
Ofcom has instructed the corporation to broadcast a peak-time declaration about its findings.
"As this represents a major infringement of our rules, we are directing the broadcaster to broadcast a announcement of our findings against it on BBC Two at nine o'clock in the evening, with a date to be finalised," the regulator stated.
'Potential to Erode Trust'
The watchdog's report stated: "Our probe found that the documentary's omission to reveal that the presenter's male guardian served in a post in the Hamas-administered government was materially misleading.
"This implied that the public did not have vital facts which may have been highly relevant to their judgment of the narrator and the details he presented.
"Credibility is at the center of the bond between a broadcaster and its audience, particularly for a public service broadcaster such as the public broadcaster.
"This oversight had the potential to erode the exceptionally strong degrees of confidence that viewers would have placed in a documentary produced by the BBC about the Israel-Gaza war."
The programme was pulled from the online platform in last February after the narrator's personal associations emerged, and in July an internal BBC review found it infringed the corporation's journalistic standards on truthfulness.
A corporation official said: "The Ofcom ruling is in accordance with the conclusions of the corporation's inquiry, that there was a major oversight in the film in relation to the broadcaster's journalistic policies on truthfulness, which aligns with clause 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we comply with Ofcom's decision in its entirety. We will adhere to the sanction as soon as the date and wording are determined."
