The British broadcaster engaged in a "major breach" of broadcasting rules by not revealing that the voice of a programme about the Gaza situation was the offspring of a Hamas administrator, as ruled by British broadcasting authority Ofcom.
An investigation by Ofcom into Gaza: How to Survive a Warzone has determined that the film was "significantly deceptive".
The BBC's director general had earlier expressed regret, stating there had been "a significant failing in relation to accuracy".
The authority has instructed the BBC to air a prime-time announcement about its conclusions.
"Given this constitutes a major infringement of our code, we are directing the corporation to broadcast a statement of our conclusions against it on BBC Two at 21:00, with a timing to be confirmed," the regulator stated.
'Potential to Erode Trust'
The watchdog's announcement said: "The inquiry we conducted found that the programme's failure to disclose that the narrator's parent served in a post in the Hamas-run administration was significantly deceptive.
"It meant that the public did not have vital facts which may have been very significant to their judgment of the voice and the information he shared.
"Credibility is at the heart of the bond between a television network and its public, notably for a state-funded media outlet such as the BBC.
"This failing had the possibility to damage the very considerable degrees of confidence that audiences would have placed in a BBC factual programme about the Israel-Gaza war."
The documentary was withdrawn from iPlayer in last February after the narrator's familial connections emerged, and in July an corporation's own inquiry determined it breached the broadcaster's content policies on factual correctness.
A BBC spokesperson said: "The regulator's decision is in agreement with the findings of Peter Johnston's review, that there was a significant failing in the documentary in relation to the broadcaster's journalistic policies on factual correctness, which aligns with regulation 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we comply with the regulator's ruling in its entirety. We will adhere to the directive as soon as the timing and wording are finalised."
