The BBC committed a "serious breach" of media regulations by not revealing that the voice of a programme about the Gaza conflict was the offspring of a Hamas official, as determined by regulatory body Ofcom.
An inquiry by the media regulator into the documentary titled Gaza: How to Survive a Warzone has found that the programme was "substantially inaccurate".
The head of the BBC had already issued an apology, saying there had been "a major oversight in relation to accuracy".
Ofcom has directed the BBC to air a evening announcement about its conclusions.
"Given this constitutes a significant violation of our code, we are directing the BBC to broadcast a announcement of our determinations against it on BBC Two at nine o'clock in the evening, with a timing to be determined," the regulator stated.
'Possibility to Undermine Credibility'
The authority's announcement said: "Our investigation determined that the film's failure to disclose that the narrator's male guardian held a post in the Hamas-administered authority was materially misleading.
"Consequently that the public did not have critical information which may have been extremely pertinent to their evaluation of the narrator and the content he presented.
"Credibility is at the core of the connection between a television network and its audience, notably for a national broadcasting corporation such as the BBC.
"This error had the possibility to erode the very considerable amounts of trust that viewers would have put in a documentary produced by the BBC about the Gaza conflict."
The documentary was removed from the online platform in February after the presenter's family links were revealed, and in the month of July an internal BBC review concluded it infringed the broadcaster's journalistic standards on accuracy.
A corporation official said: "The Ofcom ruling is in agreement with the findings of Peter Johnston's review, that there was a significant failing in the documentary in relation to the corporation's content standards on accuracy, which aligns with clause 2.2 of Ofcom's Broadcasting Code.
"We have apologised for this and we agree with the regulator's ruling in its entirety. We will follow the penalty as soon as the date and wording are finalised."
