In an escalation of their ongoing public feud, Britney Spears has sent her sister Jamie Lynn Spears a cease and desist letter to demand that she stop “referencing Britney derogatorily during your promotional campaign,” referring to a string of interviews Jamie Lynn has participated in leading up to the release of her memoir, Things I Should Have Said, on Jan 18.

Jamie Lynn has mentioned her older sister frequently in these interviews, calling the singer’s behavior before her controversial conservatorship “erratic” and even revealing one story on Nightline in which Britney allegedly locked her in a room while wielding a knife.

Britney has responded to several of these claims on social media but has now taken the complaint through an official channel with her attorney, Matthew S. Rosengart, who wrote the letter on her behalf.

“We write with some hesitation because the last thing Britney wants is to bring more attention to your ill-timed blook and its misleading or outrageous claims about her,” Rosengart begins the letter. “Although Britney has not read and doesn’t intend to read your book, she and millions of her fans were shocked to see how you have exploited her for monetary gain.”

The letter goes on to reference a line from Jamie Lynn’s book where she spoke about the difficulties of her father Jamie Spears alcoholism and claiming, “You of all people know the abuse and wrongdoing Britney had to endure during the conservatorship.”

Rosengart wrote that Jamie Lynn’s approach of “Publicly airing false or fantastical grievances is wrong, especially when designed to sell books. It is also potentially unlawful and defamatory.” The letter ends by saying that Britney will consider legal action if Jamie Lynn doesn’t stop speaking about her in interviews.

Jamie Lynn sat down with E! News yesterday, the release day of Things I Should Have Said, and referenced the feud only diplomatically. “We go back and forth, but at the end of the day, the love and support will always be there,” she said.

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