The BBC engaged in a "significant breach" of industry standards by omitting to mention that the voice of a documentary about Gaza was the offspring of a Hamas representative, as determined by regulatory body Ofcom.
An probe by the media regulator into the programme Gaza: How to Survive a Warzone has found that the programme was "materially misleading".
The chief executive of the broadcaster had already issued an apology, saying there had been "a significant failing in relation to truthfulness".
The authority has ordered the broadcaster to broadcast a prime-time declaration about its decisions.
"As this represents a serious breach of our regulations, we are instructing the corporation to transmit a message of our determinations against it on BBC2 at 21:00, with a timing to be confirmed," it said.
'Potential to Erode Confidence'
The watchdog's announcement declared: "Our investigation found that the film's failure to disclose that the voice's father served in a position in the Hamas-run government was significantly deceptive.
"This implied that the audience did not have critical information which may have been highly relevant to their assessment of the voice and the content he provided.
"Credibility is at the center of the bond between a television network and its public, particularly for a national broadcasting corporation such as the BBC.
"This oversight had the risk to undermine the significantly high amounts of credibility that viewers would have invested in a documentary produced by the BBC about the Gaza conflict."
The film was removed from the BBC's streaming service in February after the presenter's family links emerged, and in the month of July an internal BBC review determined it breached the broadcaster's content policies on truthfulness.
A corporation official commented: "The authority's determination is in agreement with the results of Peter Johnston's review, that there was a major oversight in the film in relation to the corporation's content standards on truthfulness, which reflects regulation 2.2 of the authority's broadcasting regulations.
"We issued an apology for this and we agree with Ofcom's decision in its entirety. We will follow the sanction as soon as the schedule and language are finalised."
