The BBC was found to have committed a "serious breach" of industry standards by failing to disclose that the voice of a programme about the Gaza conflict was the son of a Hamas representative, as ruled by British broadcasting authority Ofcom.
An inquiry by Ofcom into Gaza: How to Survive a Warzone has determined that the film was "substantially inaccurate".
The BBC's director general had earlier expressed regret, noting there had been "a significant failing in relation to truthfulness".
Ofcom has instructed the BBC to broadcast a peak-time announcement about its findings.
"Since this amounts to a serious breach of our regulations, we are instructing the broadcaster to broadcast a announcement of our conclusions against it on BBC Two at nine o'clock in the evening, with a date to be determined," the statement read.
'Potential to Undermine Confidence'
The regulator's announcement declared: "The inquiry we conducted concluded that the programme's lack of disclosure that the voice's parent occupied a post in the Hamas-run authority was significantly deceptive.
"This implied that the public did not have critical information which may have been highly relevant to their assessment of the voice and the information he provided.
"Trust is at the center of the relationship between a broadcaster and its viewers, notably for a state-funded media outlet such as the British Broadcasting Corporation.
"This failing had the risk to erode the exceptionally strong degrees of trust that viewers would have put in a BBC factual programme about the conflict in Gaza."
The documentary was removed from the online platform in last February after the narrator's family links emerged, and in July an internal BBC review determined it breached the broadcaster's journalistic standards on accuracy.
A BBC spokesperson commented: "The Ofcom ruling is in accordance with the results of the internal assessment, that there was a major oversight in the programme in relation to the broadcaster's journalistic policies on accuracy, which aligns with Rule 2.2 of the regulator's media standards.
"We expressed regret for this and we accept Ofcom's decision in complete. We will comply with the sanction as soon as the schedule and language are determined."
