The BBC committed a "significant breach" of industry standards by omitting to mention that the voice of a film about Gaza was the child of a Hamas official, according to regulatory body Ofcom.
An investigation by the media regulator into Gaza: How to Survive a Warzone has concluded that the documentary was "significantly deceptive".
The head of the BBC had earlier expressed regret, noting there had been "a significant failing in relation to accuracy".
The authority has ordered the corporation to transmit a evening declaration about its conclusions.
"Given this constitutes a serious breach of our code, we are directing the broadcaster to air a message of our conclusions against it on BBC Two at 21:00, with a timing to be finalised," the regulator stated.
The authority's statement stated: "Our investigation concluded that the documentary's failure to disclose that the presenter's father held a position in the Hamas-administered authority was significantly deceptive.
"This implied that the audience did not have critical information which may have been extremely pertinent to their evaluation of the narrator and the content he shared.
"Confidence is at the core of the connection between a media organization and its audience, especially for a state-funded media outlet such as the BBC.
"This oversight had the possibility to erode the significantly high amounts of trust that audiences would have invested in a BBC factual programme about the Gaza conflict."
The programme was pulled from the online platform in the month of February after the presenter's family links came to light, and in this past July an internal BBC review found it infringed the corporation's journalistic standards on accuracy.
A BBC spokesperson commented: "The regulator's decision is in line with the results of Peter Johnston's review, that there was a serious error in the documentary in relation to the BBC's Editorial Guidelines on truthfulness, which aligns with clause 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we comply with the authority's determination in complete. We will follow the sanction as soon as the timing and wording are confirmed."
