Britney Spears starts her tour in March
Britney Spears' former manager Sam Lutfi is suing the singer and her parents for libel and defamation.
The US lawsuit comes three days after a judge granted Ms Spears and her parents a restraining order against Mr Lutfi, paparazzo Adnan Ghalib and a lawyer.
Ms Spears' family have claimed Mr Lutfi had been controlling the performer's life by drugging her and taking control of her finances.
Mr Lufti said their claims have caused him "humiliation" and "distress".
He also claims in the lawsuit, filed at Los Angeles Superior Court, that he has received death threats and "has been subjected to unfathomable amounts of ridicule and public scorn".
Mr Lufti also claimed that her father Jamie Spears punched him in the chest in January, and that mother Lynne damaged his reputation by claiming he had given her daughter too much medicine.
Ms Spears has staged a successful comeback after her public breakdown.
After releasing a new album in December, she is due to start touring across the US and the UK in March.
According to her website, the singer has been "enjoying every moment of rehearsals and is looking forward to performing in front of a live audience again".