The BBC committed a "major breach" of media regulations by failing to disclose that the voice of a film about the Gaza situation was the son of a Hamas administrator, according to British broadcasting authority Ofcom.
An investigation by Ofcom into the programme Gaza: How to Survive a Warzone has found that the programme was "substantially inaccurate".
The chief executive of the broadcaster had already issued an apology, noting there had been "a major oversight in relation to accuracy".
The authority has directed the corporation to broadcast a prime-time declaration about its conclusions.
"Given this constitutes a major infringement of our rules, we are directing the BBC to transmit a announcement of our determinations against it on BBC Two at nine o'clock in the evening, with a date to be finalised," the statement read.
'Possibility to Damage Credibility'
The watchdog's report stated: "Our investigation concluded that the programme's omission to reveal that the voice's male guardian occupied a position in the Hamas-controlled authority was materially misleading.
"It meant that the viewers did not have vital facts which may have been highly relevant to their assessment of the presenter and the details he shared.
"Trust is at the heart of the relationship between a broadcaster and its audience, especially for a national broadcasting corporation such as the BBC.
"This failing had the possibility to erode the significantly high levels of credibility that audiences would have invested in a documentary produced by the BBC about the Gaza conflict."
The documentary was removed from the BBC's streaming service in February after the presenter's personal associations came to light, and in the month of July an corporation's own inquiry found it violated the broadcaster's journalistic standards on truthfulness.
A corporation official stated: "The regulator's decision is in agreement with the results of Peter Johnston's review, that there was a significant failing in the programme in relation to the BBC's Editorial Guidelines on truthfulness, which corresponds to clause 2.2 of the authority's broadcasting regulations.
"We have apologised for this and we comply with the authority's determination in full. We will comply with the directive as soon as the schedule and language are determined."
