The BBC engaged in a "significant breach" of broadcasting rules by not revealing that the presenter of a film about the Gaza situation was the son of a Hamas representative, according to UK media regulator Ofcom.
An probe by the media regulator into Gaza: How to Survive a Warzone has determined that the programme was "materially misleading".
The BBC's director general had earlier expressed regret, saying there had been "a major oversight in relation to truthfulness".
Ofcom has directed the BBC to air a prime-time declaration about its conclusions.
"Given this constitutes a major infringement of our rules, we are directing the broadcaster to air a statement of our findings against it on BBC2 at nine o'clock in the evening, with a timing to be determined," it said.
'Potential to Undermine Confidence'
The watchdog's statement declared: "The inquiry we conducted concluded that the film's lack of disclosure that the presenter's male guardian held a role in the Hamas-run administration was materially misleading.
"This implied that the viewers did not have vital facts which may have been extremely pertinent to their evaluation of the voice and the information he provided.
"Trust is at the core of the bond between a media organization and its viewers, notably for a public service broadcaster such as the British Broadcasting Corporation.
"This failing had the possibility to erode the exceptionally strong amounts 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 last February after the narrator's personal associations emerged, and in July an broadcaster's internal assessment determined it infringed the corporation's editorial guidelines on factual correctness.
A BBC spokesperson said: "The Ofcom ruling is in accordance with the results of the corporation's inquiry, that there was a serious error in the documentary in relation to the BBC's Editorial Guidelines on accuracy, which corresponds to Rule 2.2 of the authority's broadcasting regulations.
"We issued an apology for this and we comply with the regulator's ruling in full. We will follow the penalty as soon as the date and wording are finalised."
