The BBC engaged in a "serious breach" of broadcasting rules by failing to disclose that the voice of a programme about Gaza was the child of a Hamas administrator, according to UK media regulator Ofcom.
An investigation by Ofcom into Gaza: How to Survive a Warzone has determined that the programme was "substantially inaccurate".
The chief executive of the broadcaster had earlier expressed regret, saying there had been "a major oversight in relation to truthfulness".
The authority has directed the broadcaster to broadcast a prime-time declaration about its decisions.
"Given this constitutes a significant violation of our rules, we are instructing the BBC to transmit a message of our findings against it on BBC Two at 9pm, with a date to be confirmed," the regulator stated.
'Risk to Undermine Credibility'
The watchdog's announcement declared: "Our probe found that the film's omission to reveal that the presenter's parent served in a position in the Hamas-administered government was substantially inaccurate.
"It meant that the public did not have vital facts which may have been very significant to their judgment of the presenter and the information he provided.
"Credibility is at the center of the bond between a broadcaster and its audience, notably for a public service broadcaster such as the BBC.
"This oversight had the risk to undermine the exceptionally strong amounts of credibility that audiences would have placed in a documentary produced by the BBC about the conflict in Gaza."
The programme was pulled from iPlayer in February after the presenter's family links were revealed, and in July an broadcaster's internal assessment found it violated the broadcaster's journalistic standards on factual correctness.
A representative for the broadcaster commented: "The authority's determination is in agreement with the conclusions 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 reflects regulation 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we agree with the authority's determination in full. We will adhere to the penalty as soon as the schedule and wording are determined."
