Britney Spears has branded a mystery celebrity as a "piece of s***."

The 40-year-old pop star - who has become estranged from her family since a conservatorship that was governed by them was terminated in 2021 - took to Instagram on Sunday (27.11.22) to "finally" express her feelings.

Alongside an image of a mystery woman wearing dark glasses, she wrote on Instagram: "SUP BIRDS !!! Come on bitch, clap back at me for two minutes … My own party !!! Smartest one … VERY GOOD !!! You’re such a classy famous person you piece of s*** … I finally said it !!! Shade!!! I’m only human … what can I say F***YOU !!!"(sic)

The '...Baby One More Time' hitmaker did not make it clear who she was talking about, but her comments come just days after her younger sister Jamie Lynn Spears, 31, - who is known for having appeared on children's television in the late 2000s - admitted she wanted to prove she is "worth something" more than just being Britney Spears' little sister.

The former 'Zoey 101' star is taking part in the celebrity reality show 'Special Forces: World's Toughest Test', and in a teaser clip for the show, she explained she signed up as a way of stepping out of the 'Toxic' hitmaker's shadow.

Appearing dishevelled and emotional, Jamie Lynn tearfully told the trainers in the clip: "Growing up my sister [Britney] became worldwide famous.

"I guess I just want to [prove] I'm worth something."

Earlier this year, Britney - who regained control of her multimillion-dollar fortune and other aspects of her life when the arrangement came to an end - branded Jamie Lynn "scum" over the release of her autobiography 'Things I Should Have Said'.

She said: "The timing of your book was unbelievable Jamie Lynn... especially knowing the whole world had no clue what was really done to me!!!!"(sic)