The BBC committed a "significant breach" of industry standards by omitting to mention that the voice of a programme about Gaza was the offspring of a Hamas representative, according to UK media regulator Ofcom.
An probe by Ofcom into the documentary titled Gaza: How to Survive a Warzone has concluded that the film was "substantially inaccurate".
The BBC's director general had previously apologised, stating there had been "a major oversight in relation to accuracy".
Ofcom has instructed the BBC to broadcast a evening declaration about its decisions.
"Since this amounts to a major infringement of our code, we are ordering the BBC to broadcast a statement of our conclusions against it on BBC2 at 9pm, with a schedule to be determined," it said.
'Possibility to Damage Confidence'
The authority's statement stated: "The inquiry we conducted concluded that the programme's failure to disclose that the presenter's male guardian occupied a post in the Hamas-administered authority was materially misleading.
"This implied that the public did not have critical information which may have been extremely pertinent to their assessment of the voice and the information he shared.
"Trust is at the core of the connection between a broadcaster and its viewers, notably for a state-funded media outlet such as the British Broadcasting Corporation.
"This oversight had the possibility to erode the very considerable degrees of trust that viewers would have put in a factual film from the broadcaster about the Gaza conflict."
The programme was withdrawn from the BBC's streaming service in February after the narrator's familial connections emerged, and in this past July an corporation's own inquiry found it breached the broadcaster's content policies on truthfulness.
A representative for the broadcaster commented: "The regulator's decision is in line with the results of Peter Johnston's review, that there was a major oversight in the programme in relation to the BBC's Editorial Guidelines on truthfulness, which reflects Rule 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we agree with the authority's determination in complete. We will comply with the penalty as soon as the timing and language are confirmed."
