The BBC engaged in a "significant breach" of broadcasting rules by omitting to mention that the narrator of a programme about Gaza was the offspring of a Hamas representative, as determined by British broadcasting authority Ofcom.
An investigation by the media regulator into Gaza: How to Survive a Warzone has concluded that the documentary was "substantially inaccurate".
The BBC's director general had previously apologised, noting there had been "a serious error in relation to truthfulness".
Ofcom has instructed the corporation to transmit a prime-time announcement about its findings.
"Since this amounts to a serious breach of our rules, we are directing the corporation to broadcast a message of our conclusions against it on the BBC's second channel at 9pm, with a schedule to be determined," it said.
'Risk to Damage Confidence'
The watchdog's announcement said: "Our probe found that the film's lack of disclosure that the narrator's male guardian served in a position in the Hamas-run government was significantly deceptive.
"Consequently that the public did not have essential details which may have been very significant to their evaluation of the narrator and the content he provided.
"Credibility is at the center of the bond between a television network and its viewers, especially for a state-funded media outlet such as the BBC.
"This oversight had the potential to damage the exceptionally strong levels of confidence that audiences would have invested in a BBC factual programme about the Israel-Gaza war."
The documentary was pulled from the BBC's streaming service in February after the boy's family links came to light, and in this past July an internal BBC review concluded it breached the broadcaster's editorial guidelines on truthfulness.
A corporation official stated: "The regulator's decision is in line with the conclusions of the internal assessment, that there was a significant failing in the film in relation to the broadcaster's journalistic policies on accuracy, which corresponds to regulation 2.2 of Ofcom's Broadcasting Code.
"We have apologised for this and we comply with the authority's determination in complete. We will follow the sanction as soon as the timing and wording are determined."
