The public service broadcaster engaged in a "significant breach" of industry standards by not revealing that the voice of a documentary about the Gaza conflict was the son of a Hamas representative, according to British broadcasting authority Ofcom.
An probe by Ofcom into Gaza: How to Survive a Warzone has found that the programme was "substantially inaccurate".
The BBC's director general had earlier expressed regret, stating there had been "a major oversight in relation to factual correctness".
Ofcom has directed the corporation to broadcast a evening statement about its conclusions.
"Since this amounts to a major infringement of our code, we are instructing the BBC to transmit a announcement of our findings against it on BBC Two at 21:00, with a date to be confirmed," it said.
'Potential to Damage Credibility'
The watchdog's statement said: "Our investigation found that the film's lack of disclosure that the narrator's father occupied a position in the Hamas-controlled authority was significantly deceptive.
"It meant that the audience did not have vital facts which may have been highly relevant to their judgment of the narrator and the details he presented.
"Confidence is at the core of the relationship between a broadcaster and its audience, particularly for a national broadcasting corporation such as the public broadcaster.
"This oversight had the possibility to undermine the exceptionally strong levels of credibility that audiences would have invested in a documentary produced by the BBC about the conflict in Gaza."
The programme was removed from the online platform in the month of February after the presenter's familial connections were revealed, and in July an internal BBC review found it violated the corporation's journalistic standards on factual correctness.
A corporation official said: "The authority's determination is in agreement with the results of Peter Johnston's review, that there was a serious error in the film in relation to the BBC's Editorial Guidelines on truthfulness, which reflects clause 2.2 of the regulator's media standards.
"We issued an apology for this and we comply with the regulator's ruling in complete. We will comply with the penalty as soon as the timing and language are determined."
