The BBC engaged in a "major breach" of broadcasting rules by not revealing that the narrator of a film about Gaza was the offspring of a Hamas representative, as ruled by regulatory body Ofcom.
An investigation by the media regulator into Gaza: How to Survive a Warzone has found that the programme was "substantially inaccurate".
The BBC's director general had previously apologised, saying there had been "a major oversight in relation to truthfulness".
Ofcom has directed the BBC to transmit a evening declaration about its decisions.
"Given this constitutes a major infringement of our regulations, we are ordering the BBC to transmit a announcement of our determinations against it on BBC2 at 9pm, with a date to be finalised," the statement read.
'Potential to Damage Trust'
The authority's statement said: "Our investigation concluded that the documentary's omission to reveal that the narrator's father served in a post in the Hamas-administered authority was significantly deceptive.
"It meant that the public did not have vital facts which may have been extremely pertinent to their assessment of the presenter and the content he presented.
"Confidence is at the core of the connection between a television network and its viewers, notably for a state-funded media outlet such as the BBC.
"This failing had the possibility to undermine the significantly high levels of credibility that the public would have put in a documentary produced by the BBC about the conflict in Gaza."
The film was pulled from iPlayer in the month of February after the presenter's familial connections came to light, and in July an broadcaster's internal assessment found it breached the broadcaster's content policies on truthfulness.
A corporation official commented: "The Ofcom ruling is in accordance with the results of Peter Johnston's review, that there was a serious error in the film in relation to the broadcaster's journalistic policies on factual correctness, which aligns with Rule 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we comply with the authority's determination in full. We will follow the penalty as soon as the schedule and wording are determined."
