The BBC committed a "significant breach" of industry standards by omitting to mention that the narrator of a film about Gaza was the child of a Hamas administrator, as ruled by British broadcasting authority Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has determined that the documentary was "significantly deceptive".
The BBC's director general had earlier expressed regret, stating there had been "a major oversight in relation to factual correctness".
The regulator has ordered the broadcaster to transmit a prime-time declaration about its conclusions.
"As this represents a significant violation of our code, we are instructing the corporation to transmit a statement of our findings against it on BBC Two at nine o'clock in the evening, with a schedule to be finalised," it said.
'Possibility to Damage Trust'
The watchdog's statement said: "Our probe determined that the film's failure to disclose that the narrator's male guardian served in a post in the Hamas-run administration was substantially inaccurate.
"This implied that the public did not have critical information which may have been very significant to their assessment of the presenter and the content he provided.
"Confidence is at the center of the bond between a broadcaster and its audience, particularly for a national broadcasting corporation such as the British Broadcasting Corporation.
"This failing had the risk to erode the significantly high degrees of credibility that the public would have placed in a BBC factual programme about the Gaza conflict."
The programme was removed from the online platform in last February after the presenter's familial connections were revealed, and in July an corporation's own inquiry determined it violated the broadcaster's content policies on truthfulness.
A BBC spokesperson said: "The Ofcom ruling is in accordance with the conclusions of the internal assessment, that there was a significant failing in the documentary in relation to the BBC's Editorial Guidelines on factual correctness, which reflects clause 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we comply with the authority's determination in its entirety. We will adhere to the sanction as soon as the timing and wording are confirmed."
