The British broadcaster was found to have committed a "serious breach" of industry standards by not revealing that the presenter of a film about Gaza was the son of a Hamas administrator, according to regulatory body Ofcom.
An investigation by the media regulator into the programme Gaza: How to Survive a Warzone has concluded that the documentary was "substantially inaccurate".
The BBC's director general had earlier expressed regret, saying there had been "a significant failing in relation to accuracy".
Ofcom has ordered the BBC to air a evening declaration about its findings.
"Since this amounts to a major infringement of our rules, we are directing the broadcaster to air a announcement of our conclusions against it on BBC Two at 9pm, with a schedule to be finalised," it said.
'Risk to Undermine Trust'
The regulator's report said: "Our investigation concluded that the film's failure to disclose that the presenter's male guardian served in a post in the Hamas-run government was materially misleading.
"It meant that the audience did not have critical information which may have been highly relevant to their assessment of the presenter and the content he provided.
"Trust is at the core of the connection between a television network and its viewers, notably for a public service broadcaster such as the BBC.
"This failing had the possibility to erode the exceptionally strong degrees of confidence 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 February after the presenter's personal associations came to light, and in July an broadcaster's internal assessment found it breached the broadcaster's journalistic standards on factual correctness.
A corporation official said: "The Ofcom ruling is in agreement with the conclusions of Peter Johnston's review, that there was a major oversight in the programme in relation to the corporation's content standards on accuracy, which aligns with clause 2.2 of Ofcom's Broadcasting Code.
"We have apologised for this and we comply with the regulator's ruling in full. We will comply with the sanction as soon as the date and wording are determined."
