The BBC was found to have committed a "serious breach" of industry standards by failing to disclose that the presenter of a film about Gaza was the offspring of a Hamas administrator, according to regulatory body Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has found that the documentary was "significantly deceptive".
The BBC's director general had previously apologised, noting there had been "a major oversight in relation to accuracy".
Ofcom has ordered the corporation to transmit a evening declaration about its conclusions.
"Since this amounts to a serious breach of our rules, we are instructing the BBC to air a announcement of our conclusions against it on BBC2 at nine o'clock in the evening, with a schedule to be finalised," it said.
'Possibility to Damage Credibility'
The authority's report declared: "Our investigation determined that the documentary's lack of disclosure that the voice's male guardian held a position in the Hamas-controlled administration was substantially inaccurate.
"It meant that the public did not have critical information which may have been very significant to their evaluation of the voice and the information he provided.
"Confidence is at the center of the connection between a media organization and its audience, notably for a public service broadcaster such as the British Broadcasting Corporation.
"This oversight had the possibility to erode the very considerable levels of confidence that viewers would have placed in a BBC factual programme about the conflict in Gaza."
The film was withdrawn from iPlayer in last February after the narrator's familial connections emerged, and in July an corporation's own inquiry concluded it breached the organization's content policies on truthfulness.
A BBC spokesperson said: "The Ofcom ruling is in agreement with the findings of the internal assessment, that there was a significant failing in the programme in relation to the BBC's Editorial Guidelines on accuracy, which reflects regulation 2.2 of the regulator's media standards.
"We have apologised for this and we accept the authority's determination in complete. We will follow the directive as soon as the date and wording are determined."
