The BBC committed a "serious breach" of broadcasting rules by failing to disclose that the presenter of a programme about Gaza was the child of a Hamas representative, as determined by regulatory body Ofcom.
An probe by Ofcom into Gaza: How to Survive a Warzone has found that the film was "substantially inaccurate".
The chief executive of the broadcaster had earlier expressed regret, stating there had been "a major oversight in relation to truthfulness".
Ofcom has ordered the BBC to transmit a prime-time declaration about its findings.
"As this represents a significant violation of our regulations, we are directing the corporation to air a statement of our determinations against it on BBC Two at 21:00, with a schedule to be finalised," it said.
'Risk to Erode Confidence'
The watchdog's report stated: "Our investigation concluded that the documentary's failure to disclose that the narrator's parent served in a position in the Hamas-run government was substantially inaccurate.
"It meant that the audience did not have critical information which may have been extremely pertinent to their evaluation of the narrator and the content he shared.
"Trust is at the core of the relationship between a broadcaster and its audience, notably for a state-funded media outlet such as the public broadcaster.
"This failing had the potential to erode the exceptionally strong amounts of credibility that the public would have invested in a BBC factual programme about the conflict in Gaza."
The programme was withdrawn from the online platform in last February after the narrator's personal associations were revealed, and in the month of July an broadcaster's internal assessment determined it violated the corporation's editorial guidelines on factual correctness.
A BBC spokesperson said: "The Ofcom ruling is in line with the conclusions of the corporation's inquiry, that there was a significant failing in the film in relation to the broadcaster's journalistic policies on factual correctness, which reflects regulation 2.2 of the authority's broadcasting regulations.
"We issued an apology for this and we agree with Ofcom's decision in full. We will adhere to the sanction as soon as the timing and wording are confirmed."
