The BBC committed a "serious breach" of media regulations by failing to disclose that the voice of a programme about the Gaza conflict was the offspring of a Hamas official, as ruled by British broadcasting authority Ofcom.
An inquiry by the broadcasting watchdog into Gaza: How to Survive a Warzone has concluded that the film was "materially misleading".
The chief executive of the broadcaster had earlier expressed regret, stating there had been "a major oversight in relation to truthfulness".
The authority has instructed the corporation to transmit a peak-time announcement about its decisions.
"Since this amounts to a major infringement of our rules, we are ordering the corporation to transmit a message of our findings against it on the BBC's second channel at 9pm, with a schedule to be confirmed," the statement read.
'Risk to Undermine Trust'
The regulator's report stated: "The inquiry we conducted found that the documentary's failure to disclose that the narrator's male guardian served in a position in the Hamas-controlled administration was significantly deceptive.
"Consequently that the viewers did not have critical information which may have been highly relevant to their judgment of the voice and the content he shared.
"Trust is at the heart of the bond between a broadcaster and its public, especially for a public service broadcaster such as the BBC.
"This error had the risk to undermine the very considerable amounts of trust that the public would have invested in a BBC factual programme about the Gaza conflict."
The programme was removed from iPlayer in the month of February after the presenter's family links emerged, and in the month of July an internal BBC review concluded it violated the corporation's content policies on accuracy.
A BBC spokesperson stated: "The authority's determination is in accordance with the results of Peter Johnston's review, that there was a significant failing in the film in relation to the corporation's content standards on factual correctness, which corresponds to Rule 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we accept Ofcom's decision in full. We will adhere to the sanction as soon as the timing and language are confirmed."
