The BBC engaged in a "major breach" of broadcasting rules by failing to disclose that the presenter of a programme about Gaza was the son of a Hamas official, as ruled by UK media regulator Ofcom.
An inquiry by the broadcasting watchdog into the documentary titled Gaza: How to Survive a Warzone has concluded that the film was "materially misleading".
The BBC's director general had already issued an apology, saying there had been "a significant failing in relation to factual correctness".
Ofcom has directed the corporation to air a peak-time declaration about its decisions.
"Since this amounts to a major infringement of our regulations, we are directing the broadcaster to air a message of our conclusions against it on the BBC's second channel at 21:00, with a schedule to be determined," it said.
The authority's statement stated: "Our investigation concluded that the documentary's failure to disclose that the voice's male guardian held a post in the Hamas-controlled authority was materially misleading.
"Consequently that the audience did not have essential details which may have been highly relevant to their judgment of the presenter and the content he provided.
"Credibility is at the core of the bond between a television network and its audience, particularly for a national broadcasting corporation such as the BBC.
"This failing had the possibility to undermine the significantly high degrees of credibility that audiences would have invested in a documentary produced by the BBC about the Israel-Gaza war."
The programme was pulled from the BBC's streaming service in last February after the presenter's family links were revealed, and in the month of July an corporation's own inquiry found it infringed the corporation's content policies on accuracy.
A corporation official commented: "The authority's determination is in agreement with the findings of the internal assessment, that there was a significant failing in the programme in relation to the corporation's content standards on factual correctness, which corresponds to Rule 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we accept the regulator's ruling in complete. We will comply with the sanction as soon as the date and language are confirmed."
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