The footage, which shows her snorting a line of white powder from her breast, has created shock and outrage among fans of the controversial show.
While not clarifying what the substance is, Cheryl seemed to imply it was not drugs.
"I posted this video as a joke on my Instagram account several years ago," she confessed in a media statement.
"Looking back I now realise what an extremely naive thing it was to have done, and I seriously regret it."
This article originally appeared on New Idea.