The BBC engaged in a "major breach" of broadcasting rules by failing to disclose that the narrator of a film about Gaza was the child of a Hamas administrator, according to regulatory body Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has determined that the documentary was "significantly deceptive".
The BBC's director general had previously apologised, noting there had been "a major oversight in relation to truthfulness".
The regulator has instructed the corporation to transmit a prime-time declaration about its findings.
"As this represents a serious breach of our rules, we are instructing the broadcaster to transmit a announcement of our determinations against it on the BBC's second channel at 9pm, with a timing to be confirmed," the regulator stated.
'Possibility to Undermine Confidence'
The authority's statement said: "The inquiry we conducted found that the documentary's failure to disclose that the presenter's father held a post in the Hamas-controlled authority was substantially inaccurate.
"This implied that the audience did not have critical information which may have been extremely pertinent to their evaluation of the voice and the details he provided.
"Trust is at the center of the relationship between a television network and its public, notably for a national broadcasting corporation such as the public broadcaster.
"This error had the potential to undermine the significantly high degrees of credibility that viewers would have invested in a BBC factual programme about the conflict in Gaza."
The documentary was removed from the online platform in February after the narrator's family links were revealed, and in July an broadcaster's internal assessment concluded it violated the broadcaster's content policies on factual correctness.
A BBC spokesperson said: "The regulator's decision is in agreement with the results of Peter Johnston's review, that there was a significant failing in the film in relation to the BBC's Editorial Guidelines on factual correctness, which aligns with regulation 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we accept the regulator's ruling in complete. We will comply with the directive as soon as the date and language are confirmed."
