The BBC committed a "significant breach" of industry standards by not revealing that the narrator of a film about the Gaza situation was the offspring of a Hamas administrator, as ruled by UK media regulator Ofcom.
An probe by the media regulator into the programme Gaza: How to Survive a Warzone has concluded that the documentary was "significantly deceptive".
The head of the BBC had already issued an apology, noting there had been "a major oversight in relation to truthfulness".
Ofcom has instructed the broadcaster to transmit a peak-time declaration about its findings.
"As this represents a significant violation of our code, we are ordering the BBC to air a message of our findings against it on BBC2 at 9pm, with a date to be determined," it said.
The regulator's report declared: "Our investigation determined that the programme's lack of disclosure that the presenter's male guardian served in a position in the Hamas-run authority was substantially inaccurate.
"Consequently that the audience did not have essential details which may have been very significant to their assessment of the narrator and the information he provided.
"Credibility is at the heart of the bond between a television network and its audience, particularly for a state-funded media outlet such as the BBC.
"This error had the risk to undermine the very considerable amounts of trust that the public would have invested in a documentary produced by the BBC about the Gaza conflict."
The film was withdrawn from the online platform in the month of February after the narrator's familial connections came to light, and in July an internal BBC review found it breached the broadcaster's editorial guidelines on factual correctness.
A corporation official commented: "The Ofcom ruling is in line with the results of the corporation's inquiry, that there was a significant failing in the programme in relation to the broadcaster's journalistic policies on truthfulness, which aligns with Rule 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we comply with the regulator's ruling in full. We will adhere to the directive as soon as the timing and wording are determined."