The BBC committed a "major breach" of industry standards by not revealing that the narrator of a film about Gaza was the son of a Hamas official, as ruled by UK media regulator Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has concluded that the documentary was "materially misleading".
The chief executive of the broadcaster had already issued an apology, stating there had been "a serious error in relation to accuracy".
Ofcom has directed the corporation to broadcast a peak-time announcement about its conclusions.
"Since this amounts to a significant violation of our rules, we are ordering the corporation to broadcast a announcement of our findings against it on the BBC's second channel at nine o'clock in the evening, with a schedule to be determined," it said.
'Possibility to Damage Credibility'
The authority's statement stated: "Our probe determined that the film's lack of disclosure that the narrator's father served in a post in the Hamas-administered authority was significantly deceptive.
"This implied that the audience did not have vital facts which may have been very significant to their judgment of the presenter and the details he provided.
"Confidence is at the core of the relationship between a television network and its public, particularly for a state-funded media outlet such as the public broadcaster.
"This oversight had the potential to damage the significantly high levels of trust that the public would have put in a documentary produced by the BBC about the Gaza conflict."
The film was pulled from the online platform in last February after the boy's familial connections emerged, and in the month of July an corporation's own inquiry determined it violated the broadcaster's journalistic standards on factual correctness.
A corporation official said: "The regulator's decision is in accordance with the findings of the corporation's inquiry, that there was a major oversight in the documentary in relation to the broadcaster's journalistic policies on accuracy, which reflects regulation 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we comply with Ofcom's decision in complete. We will follow the penalty as soon as the schedule and language are finalised."