The BBC was found to have committed a "major breach" of media regulations by omitting to mention that the narrator of a programme about Gaza was the son of a Hamas official, according to UK media regulator Ofcom.
An investigation by Ofcom into Gaza: How to Survive a Warzone has found that the film was "substantially inaccurate".
The head of the BBC had previously apologised, stating there had been "a serious error in relation to truthfulness".
Ofcom has instructed the corporation to air a prime-time announcement about its findings.
"Given this constitutes a significant violation of our rules, we are ordering the broadcaster to air a message of our determinations against it on BBC Two at nine o'clock in the evening, with a schedule to be confirmed," the statement read.
'Possibility to Undermine Credibility'
The authority's statement said: "Our probe concluded that the documentary's failure to disclose that the voice's male guardian held a post in the Hamas-administered authority was materially misleading.
"Consequently that the viewers did not have vital facts which may have been extremely pertinent to their evaluation of the narrator and the details he presented.
"Credibility is at the core of the relationship between a broadcaster and its public, particularly for a public service broadcaster such as the BBC.
"This error had the possibility to damage the very considerable degrees of credibility that audiences would have placed in a BBC factual programme about the Gaza conflict."
The programme was removed from the online platform in the month of February after the presenter's familial connections came to light, and in July an internal BBC review concluded it breached the organization's editorial guidelines on truthfulness.
A representative for the broadcaster stated: "The Ofcom ruling is in accordance with the findings of the corporation's inquiry, that there was a major oversight in the programme in relation to the BBC's Editorial Guidelines on accuracy, which corresponds to regulation 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we comply with Ofcom's decision in its entirety. We will comply with the penalty as soon as the timing and wording are determined."
