The BBC engaged in a "significant breach" of media regulations by omitting to mention that the voice of a film about the Gaza situation was the son of a Hamas representative, as ruled by British broadcasting authority Ofcom.
An investigation by Ofcom into Gaza: How to Survive a Warzone has determined that the programme was "materially misleading".
The head of the BBC had earlier expressed regret, saying there had been "a serious error in relation to truthfulness".
The regulator has ordered the broadcaster to broadcast a prime-time declaration about its findings.
"As this represents a major infringement of our code, we are ordering the BBC to transmit a message of our determinations against it on BBC2 at 9pm, with a date to be determined," it said.
'Possibility to Undermine Trust'
The watchdog's statement said: "Our investigation concluded that the documentary's lack of disclosure that the narrator's male guardian held a role in the Hamas-controlled administration was substantially inaccurate.
"Consequently that the viewers did not have essential details which may have been extremely pertinent to their assessment of the presenter and the details he shared.
"Credibility is at the center of the relationship between a broadcaster and its audience, notably for a national broadcasting corporation such as the British Broadcasting Corporation.
"This failing had the potential to erode the very considerable amounts of trust that audiences would have put in a BBC factual programme about the conflict in Gaza."
The documentary was removed from the BBC's streaming service in last February after the boy's familial connections were revealed, and in this past July an internal BBC review determined it breached the organization's content policies on accuracy.
A corporation official commented: "The regulator's decision is in accordance with the conclusions of the corporation's inquiry, that there was a major oversight in the documentary in relation to the corporation's content standards on factual correctness, which aligns with clause 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we comply with the authority's determination in full. We will adhere to the sanction as soon as the timing and wording are finalised."
