Oops, Britney did it again.

In a clip posted by a fan on Instagram, Brittney Spears can be heard singing to Sia Furler's version of "Perfume," while performing at her Planet Hollywood Las Vegas Residency show on Saturday, according to Billboard.com.

The "Womanizer" hit maker is seen holding a microphone and walking up and down the stage while the song plays in the background. Billboard reported that Spears used Sia's track "as an in-monitor guide" when she sang, and that the track was accidentally played during the live show.

However, a representative for the mother-of-two told the Daily Mail that Spears was singing her own version of "Perfume". Sia is one of the co-writers on the track and her acoustic version of the song can be heard online, but is also found on Spears' latest album "Britney Jean". 

"She should be put on blast for this s**t. She can't f**king sing and she is making millions of dollars for doing what? Mediocre choreography and moving her mouth. It disgusts me," one fan commented on the post.

Another fan added: "Brittney spears is an overpaid joke."

In July, Spears, who is currently in the middle of her two-year "Britney: Piece of Me" stint at the Planet Hollywood Resort and Casino, came under scrutiny when a raw clip of her 2013 song "Alien" was released online - giving fans an opportunity to hear the singer's voice with no digital alterations. She was highly mocked for her out-of-tune vocals.

At the time, track producer William Orbit released a statement on Facebook claiming that the version leaked was from a "warm-up" session and not Spears' final take.

"I'd like to affirm that ANY singer when first at the mic at the start of a long session can make a multitude of vocalisations in order to get warmed up," Orbit wrote. "Warming up is essential if you're a pro, as it is with a runner doing stretches, and it takes a while to do properly. I've heard all manner of sounds emitted during warm-ups. The point is that it is not supposed to be shared with millions of listeners."

Adding: "A generous singer will put something down the mic to help the engineer get their systems warmed up and at the right level, maybe whilst having a cup of herb tea and checking through lyrics before the session really kicks off. It's not expected to be a 'take.'"