The British broadcaster committed a "significant breach" of media regulations by not revealing that the presenter of a film about Gaza was the offspring of a Hamas official, according to UK media regulator Ofcom.
An inquiry by Ofcom into Gaza: How to Survive a Warzone has determined that the film was "substantially inaccurate".
The head of the BBC had already issued an apology, stating there had been "a major oversight in relation to accuracy".
The authority has instructed the corporation to air a prime-time announcement about its conclusions.
"Given this constitutes a major infringement of our code, we are ordering the corporation to air a announcement of our determinations against it on BBC Two at nine o'clock in the evening, with a schedule to be confirmed," it said.
'Possibility to Damage Credibility'
The authority's statement declared: "Our probe found that the documentary's omission to reveal that the narrator's parent served in a role in the Hamas-administered government was significantly deceptive.
"It meant that the audience did not have vital facts which may have been very significant to their evaluation of the voice and the content he shared.
"Confidence is at the center of the relationship between a television network and its public, particularly for a public service broadcaster such as the public broadcaster.
"This failing had the risk to undermine the exceptionally strong amounts of trust that audiences would have placed in a BBC factual programme about the Israel-Gaza war."
The programme was withdrawn from the BBC's streaming service in February after the narrator's familial connections came to light, and in July an broadcaster's internal assessment concluded it violated the corporation's content policies on accuracy.
A BBC spokesperson said: "The Ofcom ruling is in agreement with the conclusions of Peter Johnston's review, that there was a significant failing in the documentary in relation to the broadcaster's journalistic policies on factual correctness, which aligns with regulation 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we comply with Ofcom's decision in full. We will comply with the sanction as soon as the schedule and language are finalised."
