The BBC engaged in a "major breach" of media regulations by omitting to mention that the presenter of a film about the Gaza conflict was the son of a Hamas official, as ruled by UK media regulator Ofcom.
An inquiry by the media regulator into Gaza: How to Survive a Warzone has found that the film was "substantially inaccurate".
The BBC's director general had earlier expressed regret, saying there had been "a serious error in relation to accuracy".
The regulator has instructed the corporation to air a peak-time statement about its conclusions.
"Since this amounts to a major infringement of our rules, we are instructing the BBC to transmit a message of our findings against it on the BBC's second channel at 21:00, with a timing to be determined," it said.
'Possibility to Undermine Trust'
The regulator's statement declared: "Our investigation determined that the documentary's failure to disclose that the narrator's parent served in a post in the Hamas-administered government was materially misleading.
"It meant that the viewers did not have vital facts which may have been very significant to their evaluation of the voice and the details he presented.
"Credibility is at the core of the relationship between a television network and its viewers, especially for a state-funded media outlet such as the public broadcaster.
"This error had the risk to undermine the exceptionally strong amounts of trust that the public would have put in a factual film from the broadcaster about the Gaza conflict."
The programme was withdrawn from the BBC's streaming service in February after the narrator's personal associations emerged, and in the month of July an internal BBC review found it infringed the organization's editorial guidelines on truthfulness.
A corporation official commented: "The regulator's decision is in accordance with the findings of the internal assessment, that there was a serious error in the programme in relation to the BBC's Editorial Guidelines on factual correctness, which corresponds to regulation 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we accept the authority's determination in full. We will comply with the penalty as soon as the date and wording are determined."
