The BBC engaged in a "major breach" of broadcasting rules by omitting to mention that the narrator of a documentary about the Gaza situation was the offspring of a Hamas administrator, according to regulatory body Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has determined that the documentary was "substantially inaccurate".
The BBC's director general had earlier expressed regret, saying there had been "a major oversight in relation to accuracy".
The regulator has directed the corporation to air a peak-time declaration about its findings.
"Given this constitutes a serious breach of our code, we are ordering the corporation to air a announcement of our findings against it on the BBC's second channel at 21:00, with a date to be confirmed," the regulator stated.
'Potential to Undermine Trust'
The watchdog's announcement stated: "The inquiry we conducted concluded that the film's omission to reveal that the voice's father occupied a post in the Hamas-controlled authority was materially misleading.
"This implied that the public did not have critical information which may have been highly relevant to their assessment of the presenter and the information he provided.
"Credibility is at the center of the bond between a media organization and its audience, notably for a public service broadcaster such as the public broadcaster.
"This failing had the possibility to erode the very considerable levels of confidence that the public would have put in a BBC factual programme about the Gaza conflict."
The documentary was withdrawn from the online platform in February after the boy's personal associations emerged, and in July an internal BBC review determined it violated the organization's journalistic standards on accuracy.
A BBC spokesperson said: "The regulator's decision is in accordance with the conclusions of Peter Johnston's review, that there was a significant failing in the film in relation to the corporation's content standards on truthfulness, which corresponds to clause 2.2 of the authority's broadcasting regulations.
"We issued an apology for this and we accept the regulator's ruling in complete. We will follow the penalty as soon as the schedule and language are finalised."
