The BBC committed a "significant breach" of industry standards by not revealing that the voice of a film about Gaza was the son of a Hamas official, as ruled by UK media regulator Ofcom.
An inquiry by Ofcom into Gaza: How to Survive a Warzone has found that the documentary was "materially misleading".
The BBC's director general had earlier expressed regret, stating there had been "a major oversight in relation to factual correctness".
Ofcom has instructed the broadcaster to broadcast a evening announcement about its conclusions.
"As this represents a significant violation of our rules, we are ordering the BBC to air a statement of our findings against it on the BBC's second channel at 9pm, with a schedule to be finalised," the statement read.
'Risk to Erode Trust'
The authority's statement declared: "The inquiry we conducted determined that the documentary's failure to disclose that the voice's parent occupied a position in the Hamas-administered authority was substantially inaccurate.
"Consequently that the public did not have essential details which may have been extremely pertinent to their judgment of the presenter and the content he presented.
"Trust is at the center of the connection between a media organization and its public, particularly for a state-funded media outlet such as the British Broadcasting Corporation.
"This error had the possibility to damage the significantly high amounts of credibility that the public would have placed in a factual film from the broadcaster about the Israel-Gaza war."
The film was removed from the BBC's streaming service in February after the presenter's family links emerged, and in the month of July an corporation's own inquiry found it infringed the corporation's content policies on truthfulness.
A corporation official said: "The authority's determination is in accordance with the conclusions of Peter Johnston's review, that there was a serious error in the programme in relation to the corporation's content standards on accuracy, which corresponds to Rule 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we comply with the regulator's ruling in its entirety. We will adhere to the penalty as soon as the timing and wording are confirmed."
