The BBC committed a "serious breach" of media regulations by omitting to mention that the voice of a programme about Gaza was the offspring of a Hamas representative, as determined by British broadcasting authority Ofcom.
An probe by Ofcom into Gaza: How to Survive a Warzone has determined that the programme was "materially misleading".
The BBC's director general had previously apologised, saying there had been "a major oversight in relation to factual correctness".
The regulator has directed the broadcaster to broadcast a evening announcement about its decisions.
"Given this constitutes a significant violation of our code, we are instructing the broadcaster to air a message of our findings against it on the BBC's second channel at 9pm, with a timing to be confirmed," the regulator stated.
'Risk to Damage Trust'
The watchdog's announcement stated: "Our probe found that the documentary's omission to reveal that the voice's male guardian occupied a role in the Hamas-administered administration was materially misleading.
"It meant that the viewers did not have essential details which may have been very significant to their evaluation of the voice and the information he provided.
"Confidence is at the center of the relationship between a broadcaster and its public, notably for a national broadcasting corporation such as the British Broadcasting Corporation.
"This oversight had the risk to erode the exceptionally strong levels of credibility that audiences would have placed in a factual film from the broadcaster about the conflict in Gaza."
The documentary was withdrawn from the BBC's streaming service in the month of February after the narrator's personal associations were revealed, and in July an corporation's own inquiry concluded it breached the corporation's content policies on truthfulness.
A BBC spokesperson stated: "The regulator's decision is in accordance with the findings of the corporation's inquiry, that there was a major oversight in the programme in relation to the BBC's Editorial Guidelines on accuracy, which corresponds to clause 2.2 of the regulator's media standards.
"We have apologised for this and we comply with the authority's determination in full. We will comply with the penalty as soon as the schedule and language are determined."
