The BBC engaged in a "serious breach" of media regulations by not revealing that the narrator of a documentary about the Gaza situation was the child of a Hamas official, as determined by British broadcasting authority Ofcom.
An probe by the media regulator into Gaza: How to Survive a Warzone has found that the documentary was "substantially inaccurate".
The chief executive of the broadcaster had earlier expressed regret, saying there had been "a major oversight in relation to factual correctness".
The authority has instructed the broadcaster to air a peak-time announcement about its findings.
"As this represents a significant violation of our rules, we are directing the corporation to air a message of our findings against it on the BBC's second channel at 9pm, with a date to be determined," it said.
'Possibility to Undermine Confidence'
The watchdog's report stated: "The inquiry we conducted found that the film's omission to reveal that the voice's male guardian held a post in the Hamas-administered administration was substantially inaccurate.
"This implied that the viewers did not have critical information which may have been highly relevant to their evaluation of the narrator and the information he presented.
"Confidence is at the heart of the relationship between a television network and its public, particularly for a state-funded media outlet such as the public broadcaster.
"This failing had the risk to erode the very considerable 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The programme was withdrawn from the BBC's streaming service in February after the boy's familial connections were revealed, and in the month of July an internal BBC review determined it violated the corporation's journalistic standards on truthfulness.
A corporation official commented: "The authority's determination is in accordance with the conclusions of Peter Johnston's review, that there was a significant failing in the film in relation to the BBC's Editorial Guidelines on truthfulness, which corresponds to clause 2.2 of the regulator's media standards.
"We issued an apology for this and we agree with the authority's determination in its entirety. We will adhere to the sanction as soon as the schedule and wording are finalised."
