The public service broadcaster engaged in a "significant breach" of media regulations by failing to disclose that the voice of a film about Gaza was the son of a Hamas administrator, according to regulatory body Ofcom.
An investigation by Ofcom into the programme Gaza: How to Survive a Warzone has concluded that the documentary was "substantially inaccurate".
The BBC's director general had already issued an apology, saying there had been "a major oversight in relation to accuracy".
Ofcom has ordered the BBC to broadcast a prime-time declaration about its findings.
"Given this constitutes a serious breach of our rules, we are ordering the BBC to air a message of our determinations against it on the BBC's second channel at nine o'clock in the evening, with a schedule to be confirmed," the statement read.
'Risk to Undermine Confidence'
The watchdog's announcement said: "Our investigation found that the programme's omission to reveal that the narrator's male guardian served in a post in the Hamas-run government was materially misleading.
"This implied that the public did not have vital facts which may have been highly relevant to their evaluation of the narrator and the content he presented.
"Credibility is at the heart of the relationship between a media organization and its viewers, notably for a state-funded media outlet such as the public broadcaster.
"This error had the risk to undermine the very considerable amounts of confidence that audiences would have put in a BBC factual programme about the Israel-Gaza war."
The film was removed from the BBC's streaming service in February after the boy's familial connections came to light, and in this past July an broadcaster's internal assessment found it breached the broadcaster's content policies on accuracy.
A BBC spokesperson commented: "The regulator's decision is in line with the results of the corporation's inquiry, that there was a serious error in the programme in relation to the corporation's content standards on factual correctness, 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 its entirety. We will comply with the sanction as soon as the timing and wording are confirmed."
