The British broadcaster was found to have committed a "major breach" of media regulations by failing to disclose that the narrator of a film about the Gaza situation was the son of a Hamas representative, as ruled by regulatory body Ofcom.
An probe by Ofcom into Gaza: How to Survive a Warzone has found that the documentary was "significantly deceptive".
The head of the BBC had already issued an apology, noting there had been "a serious error in relation to factual correctness".
The authority has ordered the BBC to transmit a peak-time announcement about its conclusions.
"Since this amounts to a serious breach of our regulations, we are instructing the broadcaster to broadcast a announcement of our conclusions against it on the BBC's second channel at 9pm, with a schedule to be confirmed," it said.
'Possibility to Undermine Trust'
The watchdog's report declared: "Our investigation found that the documentary's failure to disclose that the presenter's male guardian held a post in the Hamas-run authority was significantly deceptive.
"Consequently that the audience did not have essential details which may have been highly relevant to their judgment of the narrator and the details he shared.
"Credibility is at the heart of the connection between a television network and its public, notably for a public service broadcaster such as the BBC.
"This failing had the potential to undermine the significantly high degrees of trust that the public would have invested in a factual film from the broadcaster about the Gaza conflict."
The documentary was pulled from the BBC's streaming service in February after the narrator's family links came to light, and in July an broadcaster's internal assessment determined it infringed the organization's journalistic standards on factual correctness.
A representative for the broadcaster commented: "The Ofcom ruling is in agreement with the conclusions of the corporation's inquiry, that there was a serious error in the documentary in relation to the broadcaster's journalistic policies on truthfulness, which corresponds to Rule 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we agree with the regulator's ruling in its entirety. We will follow the sanction as soon as the date and language are determined."
