The British broadcaster engaged in a "serious breach" of media regulations by omitting to mention that the presenter of a programme about Gaza was the son of a Hamas administrator, as ruled by UK media regulator Ofcom.
An inquiry by Ofcom into the programme Gaza: How to Survive a Warzone has concluded that the programme was "significantly deceptive".
The head of the BBC had already issued an apology, noting there had been "a major oversight in relation to accuracy".
Ofcom has instructed the broadcaster to transmit a prime-time declaration about its findings.
"Since this amounts to a serious breach of our regulations, we are instructing the corporation to air a message of our determinations against it on the BBC's second channel at 9pm, with a schedule to be determined," it said.
'Potential to Erode Confidence'
The regulator's statement said: "The inquiry we conducted determined that the documentary's omission to reveal that the narrator's father held a position in the Hamas-run administration was significantly deceptive.
"Consequently that the public did not have critical information which may have been very significant to their assessment of the narrator and the information he shared.
"Credibility is at the center of the bond between a broadcaster and its viewers, notably for a state-funded media outlet such as the public broadcaster.
"This oversight had the possibility to erode the very considerable levels of credibility that the public would have invested in a documentary produced by the BBC about the conflict in Gaza."
The film was removed from the online platform in February after the boy's personal associations emerged, and in July an broadcaster's internal assessment concluded it violated the broadcaster's journalistic standards on accuracy.
A representative for the broadcaster said: "The authority's determination is in line with the findings of Peter Johnston's review, that there was a significant failing in the film in relation to the corporation's content standards on factual correctness, which corresponds to clause 2.2 of the regulator's media standards.
"We have apologised for this and we comply with the authority's determination in full. We will follow the penalty as soon as the schedule and wording are determined."
