The BBC committed a "significant breach" of media regulations by not revealing that the voice of a documentary about the Gaza conflict was the child of a Hamas official, according to UK media regulator Ofcom.
An probe by the broadcasting watchdog into Gaza: How to Survive a Warzone has determined that the documentary was "significantly deceptive".
The BBC's director general had already issued an apology, stating there had been "a significant failing in relation to accuracy".
Ofcom has instructed the broadcaster to air a evening announcement about its findings.
"As this represents a serious breach of our rules, we are directing the BBC to broadcast a announcement of our findings against it on the BBC's second channel at nine o'clock in the evening, with a timing to be determined," the statement read.
'Potential to Erode Trust'
The authority's announcement said: "The inquiry we conducted concluded that the documentary's failure to disclose that the narrator's parent held a post in the Hamas-controlled government was substantially inaccurate.
"Consequently that the public did not have vital facts which may have been extremely pertinent to their assessment of the voice and the details he shared.
"Trust is at the core of the connection between a television network and its viewers, notably for a state-funded media outlet such as the public broadcaster.
"This error had the risk to damage the significantly high amounts of trust that viewers would have placed in a factual film from the broadcaster about the Israel-Gaza war."
The film was withdrawn from iPlayer in last February after the narrator's personal associations emerged, and in July an corporation's own inquiry found it infringed the corporation's content policies on accuracy.
A corporation official stated: "The Ofcom ruling is in line with the results of Peter Johnston's review, that there was a major oversight in the programme in relation to the BBC's Editorial Guidelines on accuracy, which aligns with Rule 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we agree with the authority's determination in complete. We will comply with the penalty as soon as the schedule and wording are finalised."
