The BBC committed a "major breach" of broadcasting rules by omitting to mention that the narrator of a programme about Gaza was the offspring of a Hamas administrator, as ruled by British broadcasting authority Ofcom.
An inquiry by the media regulator into the programme Gaza: How to Survive a Warzone has determined that the documentary was "substantially inaccurate".
The BBC's director general had earlier expressed regret, saying there had been "a significant failing in relation to factual correctness".
The regulator has directed the broadcaster to broadcast a prime-time announcement about its findings.
"As this represents a significant violation of our rules, we are instructing the broadcaster to air a message of our findings against it on BBC2 at 21:00, with a schedule to be determined," it said.
'Potential to Erode Credibility'
The authority's announcement said: "Our investigation concluded that the documentary's failure to disclose that the narrator's father held a post in the Hamas-controlled government was materially misleading.
"It meant that the public did not have critical information which may have been very significant to their judgment of the presenter and the information he provided.
"Confidence is at the heart of the connection between a television network and its public, notably for a national broadcasting corporation such as the British Broadcasting Corporation.
"This failing had the potential to undermine the significantly high amounts of trust that the public would have placed in a documentary produced by the BBC about the Gaza conflict."
The programme was withdrawn from iPlayer in February after the boy's family links were revealed, and in this past July an internal BBC review concluded it violated the broadcaster's editorial guidelines on accuracy.
A BBC spokesperson commented: "The Ofcom ruling is in agreement with the findings of the corporation's inquiry, that there was a significant failing in the film in relation to the broadcaster's journalistic policies on factual correctness, which aligns with clause 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we comply with the authority's determination in its entirety. We will adhere to the sanction as soon as the timing and wording are finalised."
