The BBC engaged in a "major breach" of broadcasting rules by omitting to mention that the presenter of a programme about Gaza was the offspring of a Hamas representative, as ruled by British broadcasting authority Ofcom.
An investigation by the media regulator into the documentary titled Gaza: How to Survive a Warzone has determined that the programme was "materially misleading".
The chief executive of the broadcaster had already issued an apology, saying there had been "a major oversight in relation to accuracy".
The authority has directed the broadcaster to air a peak-time declaration about its findings.
"Since this amounts to a significant violation of our code, we are directing the broadcaster to broadcast a message of our conclusions against it on the BBC's second channel at 21:00, with a schedule to be finalised," it said.
'Possibility to Damage Confidence'
The watchdog's announcement declared: "Our investigation found that the programme's failure to disclose that the voice's male guardian held a position in the Hamas-controlled administration was substantially inaccurate.
"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 presented.
"Credibility is at the center of the relationship between a media organization and its viewers, especially for a public service broadcaster such as the public broadcaster.
"This oversight had the possibility to undermine the significantly high degrees of confidence that viewers would have invested in a BBC factual programme about the conflict in Gaza."
The documentary was pulled from the online platform in last February after the narrator's family links came to light, and in July an internal BBC review determined it breached the organization's journalistic standards on factual correctness.
A representative for the broadcaster commented: "The regulator's decision is in agreement with the results of the internal assessment, that there was a serious error in the programme in relation to the broadcaster's journalistic policies on accuracy, which aligns with regulation 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we accept Ofcom's decision in its entirety. We will follow the penalty as soon as the date and wording are determined."