The BBC engaged in a "serious breach" of media regulations by failing to disclose that the voice of a documentary about Gaza was the child of a Hamas administrator, according to British broadcasting authority Ofcom.
An inquiry by Ofcom into the documentary titled Gaza: How to Survive a Warzone has found that the programme was "substantially inaccurate".
The BBC's director general had earlier expressed regret, noting there had been "a serious error in relation to truthfulness".
The regulator has directed the corporation to transmit a evening announcement about its decisions.
"As this represents a serious breach of our rules, we are ordering the broadcaster to transmit a announcement of our conclusions against it on BBC2 at 21:00, with a timing to be determined," the statement read.
'Risk to Undermine Trust'
The regulator's report said: "Our investigation determined that the documentary's failure to disclose that the voice's male guardian served in a role in the Hamas-administered authority was materially misleading.
"This implied that the public did not have critical information which may have been extremely pertinent to their evaluation of the presenter and the details he presented.
"Credibility is at the center of the relationship between a broadcaster and its audience, especially for a state-funded media outlet such as the BBC.
"This error had the risk to undermine the very considerable amounts of trust that the public would have placed in a factual film from the broadcaster about the conflict in Gaza."
The programme was pulled from the BBC's streaming service in February after the boy's family links emerged, and in July an corporation's own inquiry found it violated the corporation's content policies on factual correctness.
A BBC spokesperson commented: "The Ofcom ruling is in accordance with the results of the corporation's inquiry, that there was a significant failing in the programme in relation to the corporation's content standards on truthfulness, which aligns with Rule 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we comply with the regulator's ruling in full. We will follow the sanction as soon as the timing and language are confirmed."
