The BBC committed a "major breach" of industry standards by failing to disclose that the voice of a programme about the Gaza situation was the son of a Hamas representative, as determined by British broadcasting authority Ofcom.
An inquiry by Ofcom into Gaza: How to Survive a Warzone has concluded that the documentary was "significantly deceptive".
The BBC's director general had previously apologised, noting there had been "a serious error in relation to factual correctness".
The regulator has instructed the broadcaster to broadcast a prime-time announcement about its conclusions.
"Since this amounts to a serious breach of our code, we are instructing the corporation to transmit a statement of our findings against it on BBC Two at 21:00, with a schedule to be finalised," the regulator stated.
'Potential to Damage Trust'
The authority's report said: "Our probe determined that the film's failure to disclose that the presenter's male guardian occupied a role in the Hamas-administered administration was substantially inaccurate.
"It meant that the viewers did not have essential details which may have been extremely pertinent to their evaluation of the voice and the content he presented.
"Trust is at the core of the connection between a media organization and its viewers, especially for a state-funded media outlet such as the British Broadcasting Corporation.
"This failing had the possibility to erode the significantly high degrees of confidence that viewers would have invested in a documentary produced by the BBC about the Israel-Gaza war."
The film was removed from the online platform in last February after the narrator's familial connections were revealed, and in July an internal BBC review found it violated the organization's editorial guidelines on truthfulness.
A corporation official commented: "The regulator's decision is in line with the conclusions of the corporation's inquiry, that there was a serious error in the film in relation to the broadcaster's journalistic policies on factual correctness, which corresponds to clause 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we accept the regulator's ruling in its entirety. We will comply with the penalty as soon as the timing and wording are finalised."
