The BBC engaged in a "significant breach" of media regulations by failing to disclose that the voice of a programme about the Gaza situation was the offspring of a Hamas representative, as determined by regulatory body Ofcom.
An probe by the broadcasting watchdog into the programme Gaza: How to Survive a Warzone has found that the programme was "significantly deceptive".
The BBC's director general had already issued an apology, noting there had been "a significant failing in relation to truthfulness".
Ofcom has ordered the BBC to transmit a evening announcement about its conclusions.
"Given this constitutes a serious breach of our regulations, we are ordering the corporation to transmit a statement of our findings against it on BBC Two at 21:00, with a schedule to be confirmed," the statement read.
'Potential to Undermine Credibility'
The authority's statement said: "The inquiry we conducted concluded that the documentary's lack of disclosure that the narrator's male guardian served in a post in the Hamas-run administration was materially misleading.
"Consequently that the audience did not have critical information which may have been very significant to their assessment of the voice and the information he shared.
"Confidence is at the heart of the relationship between a broadcaster and its viewers, particularly for a state-funded media outlet such as the public broadcaster.
"This oversight had the possibility to undermine the very considerable amounts of trust that viewers would have placed in a BBC factual programme about the conflict in Gaza."
The documentary was removed from the BBC's streaming service in February after the boy's family links came to light, and in July an broadcaster's internal assessment determined it violated the corporation's editorial guidelines on accuracy.
A BBC spokesperson said: "The regulator's decision is in agreement with the results of Peter Johnston's review, that there was a significant failing in the film in relation to the broadcaster's journalistic policies on accuracy, which corresponds to clause 2.2 of Ofcom's Broadcasting Code.
"We have apologised for this and we agree with the regulator's ruling in full. We will follow the sanction as soon as the date and language are confirmed."
