The BBC committed a "significant breach" of industry standards by failing to disclose that the voice of a film about the Gaza situation was the son of a Hamas official, as determined by UK media regulator Ofcom.
An investigation by Ofcom into the programme 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 serious error in relation to truthfulness".
The regulator has instructed the corporation to broadcast a prime-time announcement about its conclusions.
"Given this constitutes a serious breach of our rules, we are directing the broadcaster to broadcast a statement of our determinations against it on BBC2 at nine o'clock in the evening, with a date to be confirmed," it said.
'Possibility to Undermine Credibility'
The authority's announcement declared: "Our investigation found that the programme's failure to disclose that the voice's parent occupied a post in the Hamas-run authority was significantly deceptive.
"It meant that the public did not have critical information which may have been very significant to their judgment of the presenter and the details he shared.
"Confidence is at the center of the relationship between a broadcaster and its audience, particularly for a public service broadcaster such as the public broadcaster.
"This failing had the risk to damage the exceptionally strong degrees of confidence that viewers would have invested in a factual film from the broadcaster about the conflict in Gaza."
The film was withdrawn from the BBC's streaming service in February after the narrator's family links emerged, and in this past July an corporation's own inquiry determined it violated the broadcaster's editorial guidelines on factual correctness.
A corporation official said: "The authority's determination is in line with the findings of Peter Johnston's review, that there was a serious error in the film in relation to the corporation's content standards on accuracy, which reflects regulation 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 language are determined."
