The BBC engaged in a "significant breach" of media regulations by failing to disclose that the narrator of a programme about Gaza was the son of a Hamas official, as ruled by British broadcasting authority Ofcom.
An investigation by the media regulator into Gaza: How to Survive a Warzone has concluded 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 accuracy".
The authority has directed the BBC to transmit a prime-time statement about its decisions.
"Since this amounts to a significant violation of our regulations, we are directing the broadcaster to transmit a announcement of our findings against it on BBC2 at 9pm, with a date to be determined," the regulator stated.
'Potential to Undermine Credibility'
The authority's announcement said: "The inquiry we conducted concluded that the film's failure to disclose that the presenter's parent occupied a role in the Hamas-controlled administration was materially misleading.
"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 shared.
"Credibility is at the center of the bond between a broadcaster and its public, notably for a state-funded media outlet such as the British Broadcasting Corporation.
"This failing had the potential to damage the very considerable levels of confidence that viewers would have placed in a documentary produced by the BBC about the conflict in Gaza."
The programme was removed from the BBC's streaming service in February after the narrator's family links were revealed, and in the month of July an corporation's own inquiry found it infringed the organization's editorial guidelines on truthfulness.
A corporation official stated: "The Ofcom ruling is in accordance with the results 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 reflects Rule 2.2 of the regulator's media standards.
"We expressed regret for this and we agree with the authority's determination in its entirety. We will comply with the sanction as soon as the schedule and wording are confirmed."
