The BBC engaged in a "major breach" of broadcasting rules by failing to disclose that the presenter of a programme about Gaza was the child of a Hamas administrator, as ruled by British broadcasting authority Ofcom.
An inquiry by Ofcom into Gaza: How to Survive a Warzone has found that the film was "materially misleading".
The BBC's director general had earlier expressed regret, noting there had been "a serious error in relation to factual correctness".
Ofcom has directed the broadcaster to broadcast a evening declaration about its conclusions.
"Given this constitutes a significant violation of our code, we are ordering the corporation to transmit a message of our conclusions against it on BBC Two at nine o'clock in the evening, with a timing to be determined," it said.
'Possibility to Undermine Trust'
The watchdog's report stated: "Our probe found that the programme's failure to disclose that the narrator's parent served in a post in the Hamas-run administration was significantly deceptive.
"It meant that the audience did not have essential details which may have been highly relevant to their evaluation of the presenter and the content he provided.
"Trust is at the core of the bond between a television network and its audience, notably for a national broadcasting corporation such as the public broadcaster.
"This failing had the possibility to damage the exceptionally strong degrees of trust that audiences would have placed in a BBC factual programme about the Israel-Gaza war."
The documentary was pulled from iPlayer in February after the boy's familial connections came to light, and in July an corporation's own inquiry found it breached the corporation's content policies on factual correctness.
A BBC spokesperson stated: "The Ofcom ruling is in line with the conclusions of the internal assessment, that there was a serious error in the documentary in relation to the broadcaster's journalistic policies on accuracy, which reflects clause 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we comply with the regulator's ruling in complete. We will comply with the directive as soon as the date and wording are determined."
