The Pussycat Dolls' performance on The X Factor has prompted over 400 complaints.
X Factor judge Nicole Scherzinger joined her former bandmates for their first gig together in 10 years on Saturday night.
They belted out a medley of their hits together with new song react after announcing a new UK tour.
But the performance from the group - made up of Nicole, Kimberley Wyatt, Ashley Roberts, Carmit Bachar and Jessica Sutta - has seen a number of complaints.
A spokesperson for TV watchdog Ofcom said: "We’ve had 419 complaints about the Pussycat Dolls’ performance on Saturday.
"We are assessing the complaints against our broadcasting rules, but are yet to decide whether or not to investigate."
Following the performance, a defiant Nicole shared on Instagram alongside a clip: "Wasn’t expecting that... were you 😉💖"
Ahead of Saturday's show, a source had told The Sun that the group were planning to go "all out" as they took to the stage.
"The X Factor producers approached Nicole about the idea of performing with the girls and she jumped at the chance," an insider shared. “It’s going to be their first big performance of the reunion and will be extra special for Nicole because of her role in the show.
“Having the Pussycat Dolls perform is a real coup for Simon Cowell and he has told Nicole to pull out all the stops to make sure their routine gets people talking."
The X Factor: Celebrity was won on Saturday night by Megan McKenna.
She beat duo Max & Harvey, The Chase's Jenny Ryan and girl group V5 in the grand final.
The Celebrity spin-off will be followed by The X Factor: The Band from Monday night on ITV.
Airing over four episodes, Nicole and Simon Cowell will go head to head mentoring competing girl and boy bands.