The BBC committed a "serious breach" of media regulations by failing to disclose that the voice of a documentary about Gaza was the child of a Hamas administrator, as ruled by regulatory body Ofcom.
An probe by Ofcom into the documentary titled Gaza: How to Survive a Warzone has determined that the film was "significantly deceptive".
The BBC's director general had earlier expressed regret, saying there had been "a significant failing in relation to truthfulness".
The authority has instructed the corporation to transmit a peak-time announcement about its findings.
"Since this amounts to a serious breach of our rules, we are directing the corporation to air a message of our determinations against it on the BBC's second channel at nine o'clock in the evening, with a date to be determined," the regulator stated.
'Risk to Undermine Credibility'
The watchdog's announcement said: "Our investigation found that the documentary's failure to disclose that the narrator's male guardian held a position in the Hamas-controlled government was materially misleading.
"It meant that the audience did not have critical information which may have been extremely pertinent to their assessment of the presenter and the content he shared.
"Trust is at the center of the bond between a broadcaster and its audience, especially for a public service broadcaster such as the BBC.
"This failing had the risk to undermine the exceptionally strong amounts of confidence that audiences would have placed in a documentary produced by the BBC about the conflict in Gaza."
The film was pulled from iPlayer in February after the presenter's family links came to light, and in the month of July an broadcaster's internal assessment concluded it infringed the broadcaster's journalistic standards on accuracy.
A BBC spokesperson commented: "The regulator's decision is in accordance with the conclusions of Peter Johnston's review, that there was a serious error in the film in relation to the broadcaster's journalistic policies on truthfulness, which corresponds to regulation 2.2 of the regulator's media standards.
"We expressed regret for this and we comply with the authority's determination in complete. We will comply with the directive as soon as the date and wording are finalised."
