The BBC committed a "major breach" of industry standards by failing to disclose that the voice of a film about Gaza was the offspring of a Hamas representative, as ruled by UK media regulator Ofcom.
An inquiry by Ofcom into the programme Gaza: How to Survive a Warzone has concluded that the programme was "materially misleading".
The head of the BBC had already issued an apology, stating there had been "a significant failing in relation to truthfulness".
Ofcom has ordered the BBC to transmit a peak-time declaration about its findings.
"Since this amounts to a serious breach of our rules, we are directing the corporation to broadcast a message of our determinations against it on BBC Two at nine o'clock in the evening, with a timing to be confirmed," it said.
'Possibility to Erode Credibility'
The authority's announcement said: "Our investigation concluded that the film's failure to disclose that the presenter's father held a post in the Hamas-controlled government was substantially inaccurate.
"It meant that the public did not have essential details which may have been highly relevant to their assessment of the voice and the information he provided.
"Trust is at the center of the bond between a broadcaster and its public, especially for a national broadcasting corporation such as the British Broadcasting Corporation.
"This failing had the potential to undermine the very considerable degrees of confidence that viewers would have put in a factual film from the broadcaster about the Gaza conflict."
The film was removed from the BBC's streaming service in last February after the boy's familial connections were revealed, and in the month of July an internal BBC review concluded it infringed the organization's editorial guidelines on accuracy.
A representative for the broadcaster said: "The authority's determination is in accordance with the conclusions of the corporation's inquiry, that there was a serious error in the documentary in relation to the BBC's Editorial Guidelines on factual correctness, which aligns with regulation 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we comply with Ofcom's decision in complete. We will follow the sanction as soon as the date and language are determined."
