The BBC engaged in a "significant breach" of broadcasting rules by omitting to mention that the voice of a programme about Gaza was the child of a Hamas representative, as ruled by UK media regulator Ofcom.
An probe by the media regulator into Gaza: How to Survive a Warzone has found that the film was "significantly deceptive".
The head of the BBC had earlier expressed regret, saying there had been "a significant failing in relation to accuracy".
The authority has directed the BBC to air a peak-time declaration about its decisions.
"Since this amounts to a major infringement of our code, we are instructing the broadcaster to transmit a statement of our conclusions against it on BBC Two at 21:00, with a schedule to be determined," the regulator stated.
'Potential to Undermine Trust'
The authority's statement declared: "The inquiry we conducted determined that the documentary's omission to reveal that the presenter's parent held a position in the Hamas-administered authority was significantly deceptive.
"This implied that the viewers did not have critical information which may have been highly relevant to their evaluation of the presenter and the content he presented.
"Confidence is at the center of the connection between a television network and its public, especially for a state-funded media outlet such as the BBC.
"This failing had the risk to erode the very considerable amounts of confidence that viewers would have put in a documentary produced by the BBC about the Israel-Gaza war."
The film was pulled from the BBC's streaming service in last February after the narrator's familial connections came to light, and in this past July an internal BBC review determined it violated the corporation's editorial guidelines on factual correctness.
A corporation official stated: "The Ofcom ruling is in agreement with the conclusions of Peter Johnston's review, that there was a serious error in the programme in relation to the BBC's Editorial Guidelines on truthfulness, which corresponds to clause 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we accept the regulator's ruling in its entirety. We will adhere to the penalty as soon as the date and wording are confirmed."
