The BBC committed a "significant breach" of media regulations by not revealing that the presenter of a documentary about Gaza was the son of a Hamas official, as ruled by British broadcasting authority Ofcom.
An investigation by Ofcom into the programme Gaza: How to Survive a Warzone has concluded that the film was "substantially inaccurate".
The BBC's director general had previously apologised, stating there had been "a serious error in relation to accuracy".
The authority has ordered the broadcaster to air a peak-time announcement about its conclusions.
"Since this amounts to a significant violation of our code, we are ordering the broadcaster to broadcast a message of our determinations against it on BBC2 at 9pm, with a date to be determined," the statement read.
'Potential to Undermine Credibility'
The authority's report said: "Our probe found that the documentary's omission to reveal that the narrator's parent held a position in the Hamas-controlled government was materially misleading.
"Consequently that the public did not have essential details which may have been very significant to their judgment of the presenter and the information he provided.
"Confidence is at the core of the relationship between a media organization and its public, especially for a state-funded media outlet such as the BBC.
"This failing had the risk to damage the exceptionally strong levels of credibility that audiences would have placed in a BBC factual programme about the conflict in Gaza."
The documentary was pulled from the BBC's streaming service in last February after the presenter's familial connections emerged, and in July an broadcaster's internal assessment concluded it violated the organization's editorial guidelines on accuracy.
A BBC spokesperson said: "The authority's determination is in line with the findings of Peter Johnston's review, that there was a significant failing in the documentary in relation to the broadcaster's journalistic policies on accuracy, which corresponds to Rule 2.2 of the regulator's media standards.
"We issued an apology for this and we comply with the regulator's ruling in complete. We will adhere to the sanction as soon as the schedule and wording are finalised."
