'The X Factor' is to be investigated by TV watchdog Ofcom over concerns that it encouraged viewers to download songs by guest stars Diana Vickers and Michael Buble.
The regulator is to examine whether the show broke rules in the broadcasting code on references made to commercial products.
An Ofcom spokesman said: “We are investigating 'The X Factor' for potential breaches of our rules prohibiting the promotion of products in programmes.”
The media regulator is to examine two episodes of the ITV1 show.
On October 17, when Vickers – a former 'X Factor' contestant – performed, host Dermot O’Leary told viewers: “If you want to download Diana’s single, the details are at ITV.com/XFactor.
He made the same remark on the night of Canadian star Buble’s performance on October 24.
Under broadcasting rules, products and services must not be promoted in TV programmes.
The rule does not apply to programme-related material, which means that the practice is legitimate when it concerns 'X Factor' contestants but not when it relates to the promotion of guest acts.
The investigation, launched after Ofcom officials noted the references, is the latest controversy to hit the show.
Yesterday, Simon Cowell defended 'The X Factor' from claims that Sunday’s results show was a fix, saying: “We haven’t done anything wrong.”
Fans have been angered by the decision to let the judges pick which act went home from the bottom two on Sunday, leading to the departure of popular Irish contestant Mary Byrne.
Last night, 35 people were treated for minor injuries after thousands of fans braved the cold to watch 'X Factor' finalists One Direction perform.
The boy band, mentored on the ITV1 show by Cowell, performed a short open-air set in Wolverhampton’s Queen Square.