The BBC engaged in a "serious breach" of industry standards by omitting to mention that the narrator of a programme about Gaza was the child of a Hamas administrator, according to regulatory body Ofcom.
An inquiry by Ofcom into the documentary titled Gaza: How to Survive a Warzone has concluded that the programme was "significantly deceptive".
The BBC's director general had earlier expressed regret, stating there had been "a serious error in relation to truthfulness".
The authority has ordered the BBC to broadcast a prime-time declaration about its decisions.
"Given this constitutes a significant violation of our rules, we are directing the BBC to air a message of our findings against it on BBC Two at nine o'clock in the evening, with a date to be determined," the regulator stated.
'Risk to Erode Credibility'
The regulator's announcement stated: "Our investigation found that the documentary's omission to reveal that the voice's male guardian held a post in the Hamas-administered authority was significantly deceptive.
"This implied that the public did not have essential details which may have been extremely pertinent to their evaluation of the narrator and the content he provided.
"Credibility is at the center of the bond between a television network and its viewers, notably for a national broadcasting corporation such as the BBC.
"This failing had the possibility to damage the very considerable degrees of confidence that viewers would have invested in a documentary produced by the BBC about the Israel-Gaza war."
The film was removed from iPlayer in February after the presenter's familial connections came to light, and in July an corporation's own inquiry determined it violated the broadcaster's journalistic standards on truthfulness.
A BBC spokesperson stated: "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 corporation's content standards on truthfulness, which aligns with regulation 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we comply with Ofcom's decision in full. We will comply with the sanction as soon as the date and language are finalised."
