The BBC engaged in a "significant breach" of broadcasting rules by omitting to mention that the voice of a film about the Gaza situation was the son of a Hamas administrator, as ruled by British broadcasting authority Ofcom.
An probe by Ofcom into Gaza: How to Survive a Warzone has concluded that the programme was "significantly deceptive".
The head of the BBC had previously apologised, saying there had been "a major oversight in relation to accuracy".
The authority has directed the corporation to broadcast a peak-time announcement about its conclusions.
"As this represents a major infringement of our code, we are ordering the BBC to transmit a message of our conclusions against it on BBC Two at nine o'clock in the evening, with a timing to be finalised," the statement read.
'Potential to Undermine Credibility'
The regulator's statement said: "Our probe found that the programme's lack of disclosure that the presenter's father held a post in the Hamas-controlled government was significantly deceptive.
"Consequently that the viewers did not have essential details which may have been extremely pertinent to their evaluation of the narrator and the content he presented.
"Confidence is at the heart of the bond between a broadcaster and its audience, especially for a public service broadcaster such as the public broadcaster.
"This failing had the risk to damage the very considerable degrees of trust that audiences would have placed in a documentary produced by the BBC about the Gaza conflict."
The documentary was withdrawn from the BBC's streaming service in February after the presenter's personal associations were revealed, and in the month of July an internal BBC review determined it breached the organization's journalistic standards on factual correctness.
A corporation official commented: "The regulator's decision is in agreement with the conclusions of Peter Johnston's review, that there was a serious error in the documentary in relation to the broadcaster's journalistic policies on accuracy, which corresponds to Rule 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we accept Ofcom's decision in complete. We will adhere to the sanction as soon as the schedule and language are determined."
