The BBC committed a "serious breach" of media regulations by not revealing that the voice of a documentary about the Gaza conflict was the child of a Hamas official, according to regulatory body Ofcom.
An inquiry by the media regulator into the programme Gaza: How to Survive a Warzone has determined that the documentary was "materially misleading".
The BBC's director general had earlier expressed regret, noting there had been "a significant failing in relation to accuracy".
The regulator has ordered the BBC to transmit a evening announcement about its findings.
"Since this amounts to a major infringement of our code, we are instructing the corporation to air a announcement of our determinations against it on the BBC's second channel at 21:00, with a schedule to be confirmed," the regulator stated.
'Possibility to Damage Credibility'
The authority's report stated: "The inquiry we conducted determined that the film's omission to reveal that the narrator's parent served in a post in the Hamas-administered government was significantly deceptive.
"This implied that the viewers did not have vital facts which may have been very significant to their evaluation of the voice and the information he shared.
"Credibility is at the center of the relationship between a television network and its audience, notably for a national broadcasting corporation such as the public broadcaster.
"This error had the potential to damage the exceptionally strong levels of credibility that viewers would have placed in a factual film from the broadcaster about the conflict in Gaza."
The documentary was withdrawn from iPlayer in the month of February after the narrator's family links emerged, and in the month of July an broadcaster's internal assessment concluded it breached the broadcaster's editorial guidelines on truthfulness.
A corporation official commented: "The regulator's decision is in line with the results of Peter Johnston's review, that there was a major oversight in the documentary in relation to the BBC's Editorial Guidelines on accuracy, which reflects Rule 2.2 of Ofcom's Broadcasting Code.
"We have apologised for this and we agree with Ofcom's decision in its entirety. We will follow the directive as soon as the timing and wording are determined."
