The BBC engaged in a "major breach" of industry standards by omitting to mention that the voice of a documentary about the Gaza situation was the child of a Hamas administrator, as determined by UK media regulator Ofcom.
An inquiry by the media regulator into the programme Gaza: How to Survive a Warzone has concluded that the film was "materially misleading".
The BBC's director general had already issued an apology, noting there had been "a major oversight in relation to factual correctness".
Ofcom has instructed the broadcaster to transmit a prime-time announcement about its conclusions.
"Since this amounts to a major infringement of our code, we are ordering the corporation to broadcast a message of our determinations against it on BBC Two at 21:00, with a timing to be finalised," it said.
'Risk to Erode Credibility'
The watchdog's statement stated: "Our investigation determined that the film's failure to disclose that the voice's father held a post in the Hamas-controlled government was significantly deceptive.
"It meant that the audience did not have vital facts which may have been extremely pertinent to their assessment of the voice and the information he shared.
"Credibility is at the heart of the connection between a television network and its audience, particularly for a public service broadcaster such as the BBC.
"This failing had the potential to erode the very considerable amounts of trust that the public would have invested in a documentary produced by the BBC about the Israel-Gaza war."
The programme was removed from the online platform in last February after the presenter's familial connections were revealed, and in the month of July an corporation's own inquiry concluded it breached the broadcaster's journalistic standards on factual correctness.
A corporation official commented: "The regulator's decision is in accordance 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 Rule 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we comply with the regulator's ruling in its entirety. We will comply with the penalty as soon as the timing and wording are determined."
