The BBC committed a "significant breach" of industry standards by not revealing that the voice of a programme about Gaza was the offspring of a Hamas administrator, according to UK media regulator Ofcom.
An investigation by Ofcom into Gaza: How to Survive a Warzone has found that the documentary was "materially misleading".
The chief executive of the broadcaster had previously apologised, noting there had been "a major oversight in relation to factual correctness".
Ofcom has ordered the BBC to air a evening announcement about its findings.
"As this represents a major infringement of our regulations, we are directing the corporation to transmit a message of our conclusions against it on BBC Two at 9pm, with a schedule to be confirmed," it said.
'Possibility to Erode Credibility'
The authority's statement declared: "Our probe found that the documentary's omission to reveal that the narrator's male guardian served in a post in the Hamas-administered administration was substantially inaccurate.
"Consequently that the audience did not have vital facts which may have been very significant to their evaluation of the voice and the information he shared.
"Trust is at the core of the connection between a broadcaster and its public, notably for a state-funded media outlet such as the British Broadcasting Corporation.
"This error had the potential to damage the significantly high amounts of credibility that viewers would have put in a documentary produced by the BBC about the conflict in Gaza."
The film was removed from the BBC's streaming service in last February after the narrator's personal associations were revealed, and in July an internal BBC review determined it infringed the corporation's content policies on factual correctness.
A corporation official stated: "The regulator's decision is in line with the results of the internal assessment, that there was a major oversight in the programme in relation to the corporation's content standards on factual correctness, which reflects Rule 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we comply with Ofcom's decision in complete. We will follow the directive as soon as the timing and wording are determined."
