The BBC engaged in a "significant breach" of industry standards by not revealing that the voice of a film about the Gaza conflict was the child of a Hamas official, as determined by British broadcasting authority Ofcom.
An investigation by the broadcasting watchdog into the programme Gaza: How to Survive a Warzone has concluded that the film was "substantially inaccurate".
The BBC's director general had previously apologised, saying there had been "a significant failing in relation to accuracy".
Ofcom has instructed the broadcaster to broadcast a evening declaration about its conclusions.
"Given this constitutes a major infringement of our code, we are ordering the BBC to broadcast a message of our findings against it on the BBC's second channel at 9pm, with a timing to be finalised," it said.
'Potential to Undermine Credibility'
The regulator's report said: "Our probe found that the documentary's failure to disclose that the narrator's parent occupied a role in the Hamas-administered authority was substantially inaccurate.
"Consequently that the audience did not have vital facts which may have been extremely pertinent to their judgment of the narrator and the information he provided.
"Credibility is at the center of the relationship between a television network and its public, particularly for a public service broadcaster such as the public broadcaster.
"This error had the potential to undermine the significantly high amounts of credibility that viewers would have placed in a factual film from the broadcaster about the Israel-Gaza war."
The programme was removed from the BBC's streaming service in February after the narrator's personal associations came to light, and in July an broadcaster's internal assessment determined it violated the broadcaster's editorial guidelines on accuracy.
A corporation official commented: "The Ofcom ruling is in agreement with the conclusions of Peter Johnston's review, that there was a serious error in the film in relation to the BBC's Editorial Guidelines on factual correctness, which aligns with clause 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we comply with the regulator's ruling in full. We will adhere to the penalty as soon as the date and wording are finalised."
