The Advertising Standards Authority says that videos made by British vloggers on behalf of the cookie company weren’t clearly labelled as advertising.
If you're one of the 2.1 million fans of Phil Lester's AmazingPhil YouTube account, you may have seen this video from June, featuring an Oreo eating competition.
The video, which has been viewed 1.3 million times, also featured YouTuber Dan Howell (AKA danisnotonfire), a regular co-star. They take part in a "lick race challenge", which involves seeing who can remove the cream from Oreos the quickest. It was clear that Dan and Phil are big Oreo fans.
The vloggers were paid by Mondelez UK, the parent company of Oreo in the UK, to make the video, along with four other UK YouTube accounts.
And the ASA now says that that viewers would not have reasonably known that the videos were paid-for adverts. It says they should not appear again in their current form.
The ruling raises difficult questions for the current generation of British YouTube stars, who remain as marketable as they are popular.
Emma Blackery also uploaded a "LICK RACE CHALLENGE", prominently featuring Oreos and prompting other YouTubers to take up the challenge.
Popular vlogger TomSka (3.2 million followers) also did a "lick race" video as well as this elaborate "paid for advertisement", where Oreos were mentioned several times.
Someone is heard making demands of a pizza shop employee, saying: "And don't forget the pizza ... I want pepperoni on it, and pineapple, and Oreos too." He later says: "I want a million pounds and a helicopter, and put Oreos on it."
At the end, a voiceover says: "Hey you - I wanna thank Oreo for making this video possible."
