The BBC engaged in a "major breach" of broadcasting rules by not revealing that the voice of a film about Gaza was the offspring of a Hamas administrator, as ruled by regulatory body Ofcom.
An investigation by the media regulator into Gaza: How to Survive a Warzone has found that the film was "materially misleading".
The head of the BBC had earlier expressed regret, saying there had been "a major oversight in relation to factual correctness".
The regulator has ordered the BBC to air a peak-time announcement about its decisions.
"As this represents a serious breach of our regulations, we are instructing the BBC to broadcast a message of our determinations against it on the BBC's second channel at 9pm, with a timing to be determined," it said.
'Risk to Erode Credibility'
The watchdog's report stated: "Our investigation concluded that the programme's failure to disclose that the narrator's male guardian occupied a position in the Hamas-run authority was substantially inaccurate.
"It meant that the audience did not have essential details which may have been very significant to their assessment of the presenter and the content he presented.
"Trust is at the heart of the connection between a media organization and its viewers, notably for a state-funded media outlet such as the public broadcaster.
"This error had the risk to erode the exceptionally strong levels of credibility that the public would have put in a factual film from the broadcaster about the Israel-Gaza war."
The documentary was removed from the online platform in February after the narrator's personal associations emerged, and in July an broadcaster's internal assessment found it infringed the organization's content policies on truthfulness.
A corporation official said: "The Ofcom ruling is in line with the findings of Peter Johnston's review, that there was a major oversight in the programme in relation to the corporation's content standards on factual correctness, which reflects Rule 2.2 of the regulator's media standards.
"We have apologised for this and we accept Ofcom's decision in full. We will follow the directive as soon as the timing and language are confirmed."
