The BBC committed a "major breach" of broadcasting rules by not revealing that the narrator of a programme about the Gaza conflict was the son of a Hamas official, according to UK media regulator Ofcom.
An investigation by the broadcasting watchdog into Gaza: How to Survive a Warzone has determined that the programme was "materially misleading".
The head of the BBC had earlier expressed regret, saying there had been "a major oversight in relation to accuracy".
The authority has instructed the corporation to broadcast a peak-time statement about its decisions.
"As this represents a significant violation of our code, we are ordering the broadcaster to transmit a announcement of our determinations against it on the BBC's second channel at 21:00, with a timing to be determined," it said.
'Potential to Erode Trust'
The regulator's report said: "Our probe determined that the programme's lack of disclosure that the presenter's male guardian served in a role in the Hamas-controlled authority was substantially inaccurate.
"This implied that the public did not have essential details which may have been very significant to their judgment of the presenter and the information he presented.
"Credibility is at the core of the bond between a television network and its public, especially for a state-funded media outlet such as the British Broadcasting Corporation.
"This failing had the potential to erode the very considerable amounts of confidence that viewers would have placed in a BBC factual programme about the conflict in Gaza."
The documentary was pulled from the BBC's streaming service in the month of February after the presenter's personal associations came to light, and in this past July an broadcaster's internal assessment found it infringed the corporation's journalistic standards on factual correctness.
A BBC spokesperson commented: "The Ofcom ruling is in agreement with the conclusions of Peter Johnston's review, that there was a major oversight in the film in relation to the BBC's Editorial Guidelines on factual correctness, which aligns with regulation 2.2 of the authority's broadcasting regulations.
"We expressed regret for this and we agree with the regulator's ruling in its entirety. We will follow the sanction as soon as the timing and wording are finalised."
