The British broadcaster engaged in a "serious breach" of broadcasting rules by not revealing that the voice of a documentary about Gaza was the child of a Hamas official, as determined by British broadcasting authority Ofcom.
An investigation by the media regulator into the programme Gaza: How to Survive a Warzone has determined that the documentary was "materially misleading".
The BBC's director general had previously apologised, noting there had been "a serious error in relation to factual correctness".
Ofcom has ordered the corporation to air a evening declaration about its conclusions.
"Given this constitutes a serious breach of our regulations, we are directing the BBC to broadcast a announcement of our findings against it on BBC2 at nine o'clock in the evening, with a timing to be finalised," the statement read.
'Possibility to Erode Credibility'
The regulator's announcement said: "Our investigation concluded that the film's omission to reveal that the narrator's male guardian served in a role in the Hamas-run administration was materially misleading.
"This implied that the audience did not have essential details which may have been very significant to their judgment of the narrator and the information he provided.
"Confidence is at the core of the bond between a broadcaster and its viewers, particularly for a public service broadcaster such as the public broadcaster.
"This oversight had the possibility to erode the significantly high degrees of confidence that audiences would have invested in a BBC factual programme about the conflict in Gaza."
The programme was withdrawn from iPlayer in last February after the presenter's familial connections came to light, and in this past July an broadcaster's internal assessment determined it breached the broadcaster's journalistic standards on factual correctness.
A corporation official said: "The authority's determination is in agreement with the results of Peter Johnston's review, that there was a serious error in the film in relation to the broadcaster's journalistic policies on accuracy, which reflects Rule 2.2 of the regulator's media standards.
"We issued an apology for this and we comply with the authority's determination in full. We will comply with the sanction as soon as the date and language are determined."
