Britney Spears Sends Sister Jamie Lynn Cease and Desist Letter, Threatens Further Legal Action

Britney Spears is elevating her fight with her younger sister.

Britney Spears wants her younger sister to stop mentioning her or sharing stories about her while promoting her new memoir.

Jamie Lynn Spears has been sitting down for interviews and discussing her high-profile feud with the pop superstar amid the launch of her new memoir, Things I Should Have Said. 

Now, Britney' lawyer, Mathew S. Rosengart, has sent Jamie Lynn a cease and desist letter calling on the Zoey 101 alum to stop discussing her sister's life during interviews, and threatening further legal action if she refuses.

"We write with some hesitation because the last thing Britney wants is to bring more attention to your ill-timed book and its misleading or outrageous claims about her," the letter begins. "Although Britney has not read and does not intend to read your book, she and millions of her fans were shocked to see how you have exploited her for monetary gain. She will not tolerate it, nor should she."

Rosengart's letter adds, "Having endured a 13-year conservatorship that stripped her of civil rights and fundamental liberties, Britney will no longer be bullied by her father or anyone else."

"Publicly airing false or fantastical grievances is wrong, especially when designed to sell books. It is also potentially unlawful and defamatory," the letter continues. "You recently reportedly stated that the book was 'not about her.' She takes you at your word and we, therefore, demand that you cease and desist from referencing Britney derogatorily during your promotional campaign. If you fail to do so or defame her, Britney will be forced to consider and take all appropriate legal action."

The cease and desist letter comes on the heels of the first part of a two-part interview with Jamie Lynn on the Call Her Daddy podcast -- the second part of which is expected to drop on Wednesday.

Jamie Lynn first spoke about her current relationship with her sister during an interview with Nightlight that aired last week. Jamie Lynn said during the interview, "That love is still there, 100 percent. I love my sister. I've only ever loved and supported her and done what's right by her, and she knows that," Jamie Lynn tearfully told ABC News' Juju Chang. "So I don't know why we're in this position right now."

ET's Lauren Zima also spoke with the 30-year-old actress about her memoir last week, and she said a big reason why she wrote her memoir is so that she can use her voice. While she did take her sister into consideration when it came to what she shared in her book, she pointed out that it is her story.

"I think when you grow up your whole life, really, with the motto of protecting others and that became 'I wanted to protect everyone else first besides myself,' I think it’s important that I was truly open and honest and used my voice," she said. "We do have the same parents and that very much makes us sisters and I love and support my sister and I respect her healing process and however she has to work through things, and all I ask is that I, you know, have that same space because it's important. Everyone's process looks different."

"This book isn’t about me trying to clear up anything," she added. "It’s about me using my voice and showing my daughters that your voice is important -- that is what this book is about. But I hope that I guess what is happening in the recent climate, that people would understand that this is a situation that has affected many people. This is my reality that I've grown up in and it’s the only reality I know, and I’m allowed to speak about that."

For more on the lengthy, on-going public battle between the famous sisters, see the video below.