Britney Spears sends cease-and-desist to Jamie Lynn Spears over claims ahead of memoir's release

Britney Spears is escalating a war of words with her younger sister, with an attorney for the "Toxic" singer reportedly sending Jamie Lynn Spears a cease-and-desist letter.

The letter, sent Monday, according to multiple outlets, comes amid a flurry of remarks Spears's 30-year-old sister has made while promoting her memoir, "Things I Should Have Said."

"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 says, according to USA Today.

"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."

In a "Good Morning America" interview last week to promote the book, Jamie Lynn Spears denied understanding "what was happening" when a conservatorship controlled by the siblings' father, Jamie Spears, was put in place by a judge in 2008. A Los Angeles court ended the controversial 13-year conservatorship last year after the performer ripped it as "abusive" and expressed a desire to sue her family.

Since Jamie Lynn Spears's book's release, the sisters have been locked in a battle that's played out on social media. Forty-year-old Britney Spears dubbed her younger sibling "scum" following the ABC sit-down, saying her family "ruined my dreams 100 billion percent."

The cease-and-desist letter to Jamie Lynn Spears demands that the former Nickelodeon star stop "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," it said.

The letter comes ahead of a pivotal court hearing on Wednesday in Los Angeles regarding legal fees paid by Brittany Spears's estate during her conservatorship. In a court filing cited by The New York Times, Spears's lawyer said that the entertainer should not pay her father's legal expenses in an effort to close out the conservatorship, due to her allegations of misconduct against him.