The BBC committed a "major breach" of broadcasting rules by not revealing that the voice of a programme about the Gaza conflict was the son of a Hamas official, as determined by British broadcasting authority Ofcom.
An investigation by Ofcom into the programme Gaza: How to Survive a Warzone has found that the film was "substantially inaccurate".
The chief executive of the broadcaster had already issued an apology, stating there had been "a major oversight in relation to factual correctness".
The authority has instructed the corporation to transmit a prime-time declaration about its findings.
"Since this amounts to a serious breach of our regulations, we are directing the broadcaster to air a statement of our findings against it on BBC2 at 21:00, with a date to be confirmed," the regulator stated.
'Possibility to Damage Trust'
The watchdog's statement said: "The inquiry we conducted concluded that the film's failure to disclose that the voice's father occupied a role in the Hamas-run government was materially misleading.
"Consequently that the public did not have essential details which may have been extremely pertinent to their evaluation of the narrator and the information he provided.
"Trust is at the center of the relationship between a television network and its audience, notably for a state-funded media outlet such as the public broadcaster.
"This failing had the risk to undermine the exceptionally strong levels 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 last February after the presenter's personal associations were revealed, and in this past July an broadcaster's internal assessment found it breached the corporation's journalistic standards on factual correctness.
A BBC spokesperson commented: "The regulator's decision is in agreement with the findings of the corporation's inquiry, that there was a serious error in the documentary in relation to the broadcaster's journalistic policies on factual correctness, which corresponds to Rule 2.2 of the regulator's media standards.
"We issued an apology for this and we accept the authority's determination in its entirety. We will follow the sanction as soon as the schedule and wording are finalised."
