The BBC engaged in a "serious breach" of industry standards by omitting to mention that the narrator of a documentary about the Gaza situation was the offspring of a Hamas official, as determined by regulatory body Ofcom.
An inquiry by Ofcom into Gaza: How to Survive a Warzone has found that the film was "substantially inaccurate".
The chief executive of the broadcaster had already issued an apology, saying there had been "a significant failing in relation to factual correctness".
The authority has instructed the corporation to air a evening announcement about its decisions.
"As this represents a major infringement of our rules, we are ordering the broadcaster to air a message of our conclusions against it on BBC2 at 21:00, with a schedule to be confirmed," the statement read.
'Possibility to Undermine Credibility'
The authority's announcement said: "Our probe concluded that the film's failure to disclose that the presenter's father served in a role in the Hamas-administered administration was substantially inaccurate.
"This implied that the audience did not have vital facts which may have been extremely pertinent to their judgment of the voice and the information he presented.
"Confidence is at the core of the connection between a media organization and its audience, especially for a public service broadcaster such as the British Broadcasting Corporation.
"This oversight had the potential to undermine the significantly high levels of trust that audiences would have put in a documentary produced by the BBC about the Gaza conflict."
The documentary was pulled from the BBC's streaming service in the month of February after the presenter's family links came to light, and in July an broadcaster's internal assessment concluded it infringed the corporation's editorial guidelines on accuracy.
A representative for the broadcaster said: "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 BBC's Editorial Guidelines on factual correctness, which corresponds to Rule 2.2 of the authority's broadcasting regulations.
"We issued an apology for this and we agree with the authority's determination in its entirety. We will adhere to the directive as soon as the schedule and language are determined."
