The public service broadcaster engaged in a "major breach" of media regulations by not revealing that the voice of a film about the Gaza conflict was the child of a Hamas administrator, as ruled by UK media regulator Ofcom.
An probe by Ofcom into Gaza: How to Survive a Warzone has determined that the documentary was "significantly deceptive".
The BBC's director general had already issued an apology, saying there had been "a serious error in relation to truthfulness".
Ofcom has ordered the corporation to broadcast a peak-time declaration about its conclusions.
"Since this amounts to a significant violation of our rules, we are directing the broadcaster to transmit a statement of our conclusions against it on BBC Two at 9pm, with a date to be finalised," the statement read.
'Possibility to Erode Credibility'
The watchdog's announcement declared: "Our investigation determined that the documentary's failure to disclose that the narrator's father held a post in the Hamas-administered authority was materially misleading.
"This implied that the public did not have essential details which may have been very significant to their evaluation of the voice and the details he shared.
"Confidence is at the center of the relationship between a broadcaster and its viewers, particularly for a public service broadcaster such as the public broadcaster.
"This failing had the potential to erode the very considerable levels of confidence that the public would have put in a factual film from the broadcaster about the Israel-Gaza war."
The documentary was withdrawn from the BBC's streaming service in last February after the boy's family links emerged, and in July an corporation's own inquiry concluded it violated the broadcaster's editorial guidelines on truthfulness.
A corporation official commented: "The regulator's decision is in line with the results of the internal assessment, that there was a significant failing in the programme in relation to the BBC's Editorial Guidelines on accuracy, which corresponds to clause 2.2 of the regulator's media standards.
"We have apologised for this and we accept the authority's determination in its entirety. We will follow the penalty as soon as the timing and language are confirmed."
