The BBC committed a "serious breach" of media regulations by failing to disclose that the voice of a film about Gaza was the son of a Hamas representative, according to regulatory body Ofcom.
An probe by the broadcasting watchdog into Gaza: How to Survive a Warzone has determined that the film was "materially misleading".
The BBC's director general had previously apologised, saying there had been "a significant failing in relation to accuracy".
The authority has instructed the corporation to air a peak-time announcement about its conclusions.
"Since this amounts to a major infringement of our code, we are ordering the BBC to broadcast a announcement of our determinations against it on BBC2 at 21:00, with a date to be determined," it said.
'Possibility to Erode Trust'
The watchdog's announcement said: "The inquiry we conducted determined that the documentary's lack of disclosure that the narrator's male guardian occupied a position in the Hamas-controlled government was materially misleading.
"Consequently that the audience did not have vital facts which may have been highly relevant to their assessment of the voice and the information he provided.
"Credibility is at the center of the bond between a broadcaster and its viewers, particularly for a national broadcasting corporation such as the public broadcaster.
"This error had the potential to erode the exceptionally strong degrees of confidence that the public would have invested in a BBC factual programme about the Gaza conflict."
The film was withdrawn from the online platform in last February after the narrator's family links emerged, and in the month of July an internal BBC review found it violated the organization's journalistic standards on factual correctness.
A representative for the broadcaster stated: "The Ofcom ruling is in accordance with the results of the internal assessment, that there was a significant failing in the programme in relation to the corporation's content standards on accuracy, which reflects clause 2.2 of the authority's broadcasting regulations.
"We issued an apology for this and we agree with Ofcom's decision in full. We will follow the sanction as soon as the date and wording are determined."
