The pair's performances, which included duets with the talent show's finalists as well as their own solo slots, were said to be unsuitable for pre-watershed viewing, leading to over one thousand complaints from viewers, the Daily Mail reports.
Vivienne Pattison, director of Mediawatch UK, said: "I don’t think it was suitable for a pre-watershed broadcast, I think that’s quite clear.
"It was the simulated sexual stuff, that was the problem. I think Ofcom should look into this. Whether The X Factor like it or not they are commanding audiences of more than 19 million.
"They are role models whether they like it or not."
An investigation by the Office of Communications is said to have been launched.