The public service broadcaster committed a "significant breach" of broadcasting rules by not revealing that the narrator of a documentary about the Gaza situation was the offspring of a Hamas official, as determined by British broadcasting authority Ofcom.
An probe by the broadcasting watchdog into the programme Gaza: How to Survive a Warzone has determined that the documentary was "substantially inaccurate".
The BBC's director general had previously apologised, saying there had been "a major oversight in relation to truthfulness".
The regulator has directed the BBC to transmit a evening announcement about its conclusions.
"As this represents a significant violation of our code, we are instructing the BBC to transmit a statement of our findings against it on BBC Two at 9pm, with a date to be finalised," it said.
'Potential to Erode Trust'
The regulator's report stated: "The inquiry we conducted found that the documentary's omission to reveal that the voice's male guardian served in a position in the Hamas-controlled authority was substantially inaccurate.
"It meant that the public did not have vital facts which may have been highly relevant to their judgment of the voice and the content he presented.
"Confidence is at the core of the relationship between a broadcaster and its viewers, particularly for a national broadcasting corporation such as the British Broadcasting Corporation.
"This failing had the possibility to damage the significantly high levels of credibility that audiences would have put in a factual film from the broadcaster about the conflict in Gaza."
The film was pulled from iPlayer in last February after the narrator's family links emerged, and in July an corporation's own inquiry concluded it violated the broadcaster's editorial guidelines on accuracy.
A representative for the broadcaster commented: "The authority's determination is in line with the results of Peter Johnston's review, that there was a serious error in the film in relation to the BBC's Editorial Guidelines on accuracy, which reflects regulation 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we accept the regulator's ruling in its entirety. We will follow the penalty as soon as the date and wording are finalised."
