The BBC engaged in a "major breach" of media regulations by not revealing that the voice of a film about Gaza was the son of a Hamas representative, according to British broadcasting authority Ofcom.
An inquiry by Ofcom into the programme Gaza: How to Survive a Warzone has found that the programme was "substantially inaccurate".
The head of the BBC had earlier expressed regret, noting there had been "a major oversight in relation to factual correctness".
The regulator has instructed the broadcaster to air a prime-time announcement about its conclusions.
"Since this amounts to a major infringement of our regulations, we are instructing the broadcaster to broadcast a message of our determinations against it on BBC Two at 21:00, with a timing to be confirmed," it said.
'Risk to Undermine Credibility'
The regulator's statement declared: "Our investigation concluded that the film's omission to reveal that the presenter's male guardian held a role in the Hamas-controlled administration was significantly deceptive.
"This implied that the audience did not have critical information which may have been extremely pertinent to their assessment of the voice and the details he presented.
"Confidence is at the core of the relationship between a media organization and its viewers, notably for a national broadcasting corporation such as the British Broadcasting Corporation.
"This failing had the possibility to erode the exceptionally strong levels of credibility that viewers would have invested in a factual film from the broadcaster about the Gaza conflict."
The programme was pulled from the BBC's streaming service in last February after the narrator's personal associations came to light, and in this past July an internal BBC review determined it violated the broadcaster's editorial guidelines on factual correctness.
A corporation official stated: "The Ofcom ruling is in agreement with the findings of Peter Johnston's review, that there was a serious error in the documentary in relation to the broadcaster's journalistic policies on truthfulness, which reflects Rule 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we agree with Ofcom's decision in complete. We will adhere to the penalty as soon as the date and wording are determined."
