The BBC committed a "significant breach" of broadcasting rules by omitting to mention that the presenter of a documentary about the Gaza situation was the son of a Hamas official, as determined by British broadcasting authority Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has determined that the programme was "significantly deceptive".
The BBC's director general had earlier expressed regret, noting there had been "a significant failing in relation to accuracy".
The authority has directed the corporation to broadcast a peak-time declaration about its conclusions.
"Given this constitutes a serious breach of our regulations, we are directing the broadcaster to air a message of our determinations against it on BBC Two at 21:00, with a date to be determined," it said.
The authority's statement stated: "The inquiry we conducted found that the documentary's lack of disclosure that the presenter's parent held a post in the Hamas-administered administration was significantly deceptive.
"Consequently that the viewers did not have critical information which may have been extremely pertinent to their assessment of the narrator and the information he presented.
"Confidence is at the heart of the connection between a broadcaster and its public, especially for a state-funded media outlet such as the BBC.
"This failing had the risk to damage the exceptionally strong amounts of confidence that viewers would have put in a factual film from the broadcaster about the Gaza conflict."
The film was withdrawn from iPlayer in the month of February after the boy's familial connections emerged, and in July an corporation's own inquiry determined it breached the organization's content policies on truthfulness.
A BBC spokesperson said: "The authority's determination is in line with the results of the internal assessment, that there was a major oversight in the documentary in relation to the BBC's Editorial Guidelines on factual correctness, which corresponds to clause 2.2 of the regulator's media standards.
"We expressed regret for this and we comply with the authority's determination in full. We will adhere to the penalty as soon as the date and wording are finalised."
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