The BBC engaged in a "serious breach" of media regulations by omitting to mention that the narrator of a programme about the Gaza situation was the child of a Hamas administrator, according to regulatory body Ofcom.
An probe by the media regulator into Gaza: How to Survive a Warzone has found that the programme was "materially misleading".
The BBC's director general had earlier expressed regret, saying there had been "a serious error in relation to factual correctness".
The regulator has instructed the corporation to transmit a prime-time announcement about its findings.
"Since this amounts to a significant violation of our code, we are ordering the broadcaster to broadcast a message of our findings against it on the BBC's second channel at nine o'clock in the evening, with a schedule to be confirmed," it said.
'Possibility to Erode Credibility'
The authority's announcement said: "The inquiry we conducted found that the programme's lack of disclosure that the voice's parent served in a role in the Hamas-run government was substantially inaccurate.
"This implied that the viewers did not have critical information which may have been highly relevant to their judgment of the voice and the content he provided.
"Credibility is at the core of the connection between a broadcaster and its viewers, notably for a national broadcasting corporation such as the British Broadcasting Corporation.
"This error had the potential to erode the significantly high levels of credibility that the public would have put in a BBC factual programme about the Israel-Gaza war."
The film was removed from the online platform in last February after the narrator's family links were revealed, and in July an broadcaster's internal assessment found it breached the broadcaster's journalistic standards on truthfulness.
A representative for the broadcaster said: "The authority's determination is in line with the results of the internal assessment, that there was a serious error in the documentary in relation to the corporation's content standards on truthfulness, which aligns with clause 2.2 of the regulator's media standards.
"We have apologised for this and we accept Ofcom's decision in complete. We will follow the sanction as soon as the schedule and language are determined."
