The BBC committed a "serious breach" of broadcasting rules by failing to disclose that the voice of a film about Gaza was the son of a Hamas representative, according to British broadcasting authority Ofcom.
An investigation by Ofcom into Gaza: How to Survive a Warzone has concluded that the film was "substantially inaccurate".
The head of the BBC had already issued an apology, saying there had been "a serious error in relation to truthfulness".
Ofcom has ordered the broadcaster to transmit a evening declaration about its findings.
"As this represents a major infringement of our regulations, we are directing the broadcaster to broadcast a statement of our findings against it on BBC Two at 9pm, with a schedule to be determined," the regulator stated.
The watchdog's report said: "Our investigation concluded that the programme's omission to reveal that the presenter's parent occupied a position in the Hamas-controlled administration was substantially inaccurate.
"This implied that the audience did not have essential details which may have been highly relevant to their evaluation of the narrator and the content he presented.
"Credibility is at the core of the bond between a media organization and its viewers, notably for a state-funded media outlet such as the British Broadcasting Corporation.
"This oversight had the possibility to damage the significantly high amounts of credibility that audiences would have invested in a factual film from the broadcaster about the conflict in Gaza."
The film was pulled from the BBC's streaming service in last February after the presenter's family links came to light, and in the month of July an internal BBC review found it infringed the broadcaster's journalistic standards on accuracy.
A representative for the broadcaster commented: "The Ofcom ruling is in agreement with the conclusions of Peter Johnston's review, that there was a major oversight in the programme in relation to the corporation's content standards on accuracy, which aligns with Rule 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we agree with the regulator's ruling in its entirety. We will comply with the penalty as soon as the date and language are finalised."
Lena Voss is a tech journalist and digital strategist with a passion for uncovering emerging trends.