The BBC was found to have committed a "significant breach" of media regulations by not revealing that the presenter of a programme about Gaza was the son of a Hamas administrator, as ruled by British broadcasting authority Ofcom.
An investigation by the broadcasting watchdog into Gaza: How to Survive a Warzone has found that the film was "substantially inaccurate".
The head of the BBC had already issued an apology, saying there had been "a serious error in relation to factual correctness".
The regulator has directed the corporation to air a evening announcement about its conclusions.
"Given this constitutes a significant violation of our rules, we are directing the BBC to transmit a announcement of our conclusions against it on BBC Two at nine o'clock in the evening, with a timing to be confirmed," the regulator stated.
'Potential to Undermine Trust'
The authority's statement stated: "Our probe concluded that the documentary's failure to disclose that the voice's male guardian held a post in the Hamas-run administration was materially misleading.
"Consequently that the viewers did not have critical information which may have been highly relevant to their evaluation of the voice and the information he presented.
"Confidence is at the core of the connection between a media organization and its viewers, especially for a public service broadcaster such as the British Broadcasting Corporation.
"This failing had the possibility to erode the exceptionally strong amounts of credibility that audiences would have invested in a factual film from the broadcaster about the conflict in Gaza."
The documentary was removed from the BBC's streaming service in February after the narrator's familial connections were revealed, and in July an broadcaster's internal assessment determined it breached the organization's journalistic standards on truthfulness.
A BBC spokesperson stated: "The Ofcom ruling is in line with the results of the internal assessment, that there was a major oversight in the film in relation to the corporation's content standards on factual correctness, which reflects 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 follow the sanction as soon as the date and wording are confirmed."
