The BBC engaged in a "serious breach" of media regulations by not revealing that the voice of a programme about Gaza was the offspring of a Hamas administrator, as determined by UK media regulator Ofcom.
An inquiry by Ofcom into the programme Gaza: How to Survive a Warzone has found that the film was "materially misleading".
The BBC's director general had earlier expressed regret, noting there had been "a significant failing in relation to accuracy".
Ofcom has directed the BBC to broadcast a evening announcement about its conclusions.
"Since this amounts to a serious breach of our regulations, we are directing the BBC to air a statement of our findings against it on BBC2 at 21:00, with a schedule to be determined," it said.
'Possibility to Undermine Trust'
The regulator's statement stated: "Our probe concluded that the film's failure to disclose that the presenter's parent occupied a post in the Hamas-run authority was materially misleading.
"Consequently that the public did not have essential details which may have been extremely pertinent to their judgment of the presenter and the content he provided.
"Confidence is at the center of the relationship between a broadcaster and its public, especially for a national broadcasting corporation such as the BBC.
"This error had the risk to damage the very considerable degrees of credibility that audiences would have invested in a factual film from the broadcaster about the Gaza conflict."
The documentary was removed from the BBC's streaming service in last February after the narrator's familial connections emerged, and in July an corporation's own inquiry determined it infringed the corporation's content policies on truthfulness.
A corporation official said: "The authority's determination is in line with the conclusions of Peter Johnston's review, that there was a significant failing in the documentary in relation to the BBC's Editorial Guidelines on truthfulness, which aligns with Rule 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we comply with the regulator's ruling in its entirety. We will adhere to the penalty as soon as the schedule and language are finalised."
