The BBC committed a "major breach" of industry standards by failing to disclose that the voice of a programme about Gaza was the offspring of a Hamas administrator, as ruled by regulatory body Ofcom.
An probe by Ofcom into the programme Gaza: How to Survive a Warzone has determined that the programme was "significantly deceptive".
The BBC's director general had previously apologised, saying there had been "a significant failing in relation to factual correctness".
The regulator has directed the corporation to transmit a prime-time declaration about its findings.
"Given this constitutes a major infringement of our regulations, we are instructing the BBC to transmit a statement of our determinations against it on the BBC's second channel at 21:00, with a timing to be determined," the regulator stated.
'Risk to Erode Trust'
The regulator's report stated: "Our investigation found that the film's failure to disclose that the presenter's male guardian held a post in the Hamas-controlled administration was materially misleading.
"This implied that the viewers did not have essential details which may have been very significant to their evaluation of the voice and the content he shared.
"Trust is at the heart of the relationship between a television network and its audience, particularly for a state-funded media outlet such as the British Broadcasting Corporation.
"This error had the risk to erode the exceptionally strong levels of credibility that viewers would have put in a documentary produced by the BBC about the Gaza conflict."
The documentary was withdrawn from the online platform in February after the narrator's personal associations came to light, and in the month of July an corporation's own inquiry concluded it infringed the broadcaster's editorial guidelines on factual correctness.
A BBC spokesperson said: "The Ofcom ruling is in line with the results of the corporation's inquiry, that there was a major oversight in the documentary in relation to the broadcaster's journalistic policies on truthfulness, which aligns with Rule 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we comply with the regulator's ruling in its entirety. We will comply with the penalty as soon as the date and wording are determined."
