The BBC committed a "major breach" of broadcasting rules by failing to disclose that the presenter of a documentary about the Gaza conflict was the son of a Hamas administrator, as ruled by regulatory body Ofcom.
An probe by the broadcasting watchdog into Gaza: How to Survive a Warzone has determined that the film was "substantially inaccurate".
The head of the BBC had earlier expressed regret, noting there had been "a significant failing in relation to factual correctness".
The authority has ordered the BBC to air a peak-time announcement about its conclusions.
"Given this constitutes a serious breach of our regulations, we are instructing the BBC to air a announcement of our conclusions against it on the BBC's second channel at nine o'clock in the evening, with a date to be determined," the statement read.
'Possibility to Undermine Credibility'
The regulator's report said: "The inquiry we conducted determined that the programme's omission to reveal that the voice's parent held a role in the Hamas-controlled administration was materially misleading.
"Consequently that the audience did not have critical information which may have been extremely pertinent to their assessment of the presenter and the content he shared.
"Confidence is at the center of the bond between a media organization and its audience, notably for a national broadcasting corporation such as the BBC.
"This error had the potential to erode the very considerable levels of confidence that viewers would have placed in a documentary produced by the BBC about the Gaza conflict."
The film was pulled from the BBC's streaming service in last February after the narrator's family links emerged, and in this past July an internal BBC review concluded it breached the organization's journalistic standards on truthfulness.
A BBC spokesperson said: "The regulator's decision is in agreement with the findings of Peter Johnston's review, that there was a serious error in the film in relation to the broadcaster's journalistic policies on accuracy, which reflects Rule 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we agree with the authority's determination in full. We will follow the sanction as soon as the timing and language are determined."
