The BBC committed a "significant breach" of media regulations by omitting to mention that the voice of a film about the Gaza situation was the offspring of a Hamas official, according to UK media regulator Ofcom.
An inquiry by the broadcasting watchdog into Gaza: How to Survive a Warzone has found that the documentary was "substantially inaccurate".
The chief executive of the broadcaster had earlier expressed regret, noting there had been "a major oversight in relation to truthfulness".
The regulator has instructed the corporation to transmit a evening statement about its decisions.
"Given this constitutes a serious breach of our code, we are directing the corporation to air a message of our determinations against it on BBC Two at 9pm, with a timing to be determined," the statement read.
'Potential to Erode Trust'
The watchdog's report declared: "Our investigation determined that the documentary's lack of disclosure that the presenter's male guardian occupied a position in the Hamas-run authority was materially misleading.
"This implied that the audience did not have critical information which may have been extremely pertinent to their judgment of the presenter and the information he shared.
"Trust is at the center of the bond between a media organization and its audience, notably for a state-funded media outlet such as the BBC.
"This oversight had the possibility to erode the significantly high levels of trust that audiences would have put in a BBC factual programme about the Israel-Gaza war."
The film was pulled from iPlayer in last February after the narrator's familial connections emerged, and in this past July an broadcaster's internal assessment determined it breached the organization's content policies on truthfulness.
A BBC spokesperson said: "The authority's determination is in agreement with the conclusions of the corporation's inquiry, that there was a significant failing in the documentary in relation to the broadcaster's journalistic policies on truthfulness, which reflects regulation 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we accept the authority's determination in its entirety. We will comply with the sanction as soon as the date and wording are determined."
