The BBC was found to have committed a "significant breach" of media regulations by not revealing that the narrator of a documentary about the Gaza situation was the child of a Hamas representative, as ruled by British broadcasting authority Ofcom.
An investigation by Ofcom into Gaza: How to Survive a Warzone has concluded that the programme was "materially misleading".
The head of the BBC had previously apologised, noting there had been "a major oversight in relation to accuracy".
Ofcom has ordered the corporation to transmit a prime-time declaration about its conclusions.
"Since this amounts to a serious breach of our code, we are ordering the BBC to transmit a announcement of our conclusions against it on BBC Two at nine o'clock in the evening, with a date to be confirmed," it said.
'Possibility to Undermine Credibility'
The watchdog's report said: "Our investigation concluded that the film's failure to disclose that the presenter's male guardian held a role in the Hamas-administered authority was substantially inaccurate.
"It meant that the public did not have essential details which may have been highly relevant to their assessment of the presenter and the details he presented.
"Trust is at the core of the connection between a broadcaster and its viewers, notably for a state-funded media outlet such as the public broadcaster.
"This oversight had the risk to damage the exceptionally strong levels of credibility that the public would have invested in a documentary produced by the BBC about the conflict in Gaza."
The documentary was withdrawn from the BBC's streaming service in last February after the presenter's family links emerged, and in July an broadcaster's internal assessment found it infringed the organization's editorial guidelines on accuracy.
A corporation official said: "The Ofcom ruling is in line with the findings of the internal assessment, that there was a serious error in the film in relation to the broadcaster's journalistic policies on factual correctness, which corresponds to regulation 2.2 of the regulator's media standards.
"We have apologised for this and we accept the regulator's ruling in full. We will follow the penalty as soon as the timing and language are determined."
