The BBC was found to have committed a "serious breach" of broadcasting rules by omitting to mention that the voice of a film about Gaza was the child of a Hamas official, according to regulatory body Ofcom.
An inquiry by Ofcom into Gaza: How to Survive a Warzone has concluded that the programme was "materially misleading".
The head of the BBC had earlier expressed regret, saying there had been "a serious error in relation to truthfulness".
The authority has instructed the corporation to air a evening announcement about its decisions.
"Given this constitutes a significant violation of our regulations, we are instructing the BBC to broadcast a announcement of our findings against it on BBC Two at 21:00, with a schedule to be finalised," the regulator stated.
'Potential to Undermine Trust'
The watchdog's announcement said: "The inquiry we conducted concluded that the programme's omission to reveal that the narrator's father served in a position in the Hamas-run authority was substantially inaccurate.
"Consequently that the public did not have essential details which may have been extremely pertinent to their assessment of the presenter and the details he presented.
"Trust is at the core of the bond between a television network and its audience, particularly for a national broadcasting corporation such as the BBC.
"This oversight had the risk to damage the very considerable amounts of trust that viewers would have placed in a documentary produced by the BBC about the Gaza conflict."
The documentary was pulled from the BBC's streaming service in last February after the boy's family links came to light, and in July an broadcaster's internal assessment concluded it breached the organization's editorial guidelines on truthfulness.
A BBC spokesperson commented: "The authority's determination is in agreement with the findings of Peter Johnston's review, that there was a significant failing in the film in relation to the broadcaster's journalistic policies on truthfulness, which aligns with Rule 2.2 of Ofcom's Broadcasting Code.
"We expressed regret for this and we comply with the authority's determination in full. We will follow the penalty as soon as the date and wording are confirmed."
