The BBC said a trailer screened Wednesday for a forthcoming documentary showed the queen arriving at, and not departing, the sitting.
The scene showed the queen walking down a corridor, wearing a crown and her Order of the Garter robes, and telling her lady-in-waiting: "I'm not changing anything. I've had enough dressing like this, thank you very much."
"In this trailer there is a sequence that implies that the queen left a sitting prematurely," the BBC said.
"This was not the case, and the actual sequence of events was misrepresented. The BBC would like to apologize to both the queen and Annie Leibovitz for any upset this may have caused."
The promotional footage showed the queen balking at the photographer's request that she remove her crown.
Leibovitz told the queen: "I think it will look better without the crown because the garter robe is so..."
The queen cut her off with an icy stare.
"Less dressy! What do you think this is?" the monarch said, gesturing to her attire.
The BBC Trust, the corporation's new governance body, said it has asked BBC Director General Mark Thompson to provide a full explanation of how the mistake was made.
The BBC also issued a statement Thursday night saying the footage was shown by mistake.
It said the production company RDF Media had made the faulty footage several months ago and that it was never intended to be seen by the public or the media. The BBC said it was mistakenly given to the network for the promotion of the forthcoming documentary.