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Britney Spears is taking action.

The 40-year-old pop star and her attorney Mathew Rosengart have taken legal action against her father Jamie and sister Jamie Lynn as the court battle regarding her 13-year conservatorship drudges on.

Fox News Digital obtained a cease-and-desist letter that Rosengart sent Jamie Lynn on Monday, telling her to "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." Jamie Lynn is promoting her upcoming book, "Things I Should Have Said."

"We write with 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 continues.

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Britney Spears

Britney Spears has taken legal action against her father, Jamie, and sister, Jamie Lynn. (Steve Jennings/WireImage)

Rosengart added that his client has no intention to read the book but is shocked that Jamie Lynn has "exploited her for monetary gain."

"She will not tolerate it, nor should she," the attorney stated.

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He continued: "You of all people know the abuse and wrongdoing Britney had to endure during the conservatorship, after initially growing up with a 'ruinous,' alcoholic father."

Jamie Spears

Britney Spears requested that her father, Jamie, return millions of dollars that he earned over the course of her 13-year conservatorship. (Nick Ut)

Taking another shot at the country star, Rosengart added, "Britney was the family's breadwinner and she also otherwise supported you. Publicly airing false or fantastical grievances is wrong, especially when designed to sell books. It is also potentially unlawful and defamatory."

Additionally, citing court docs, TMZ reports that Britney Spears is requesting that millions of dollars that her father made during the conservatorship be returned to her – the docs allege that Jamie made $6 million over the course of the legal guardianship.

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The docs reportedly also allege Jamie "engaged in self-dealing, financial and business mismanagement ... engaged in abusive and bullying conduct toward his daughter, [and] deprived his daughter of fundamental civil liberties …" per the outlet.

Jamie Lynn Spears

Britney Spears' sister, Jamie Lynn, also received a cease-and-desist letter regarding how she addresses Britney amid her promotional tour for her book "Things I Should Have Said."  ( John Shearer/WireImage)

Part of the $6 million that Jamie earned was used to pitch a television show called "Cookin' Cruzin' & Chaos," the docs state, per the outlet. Additionally, Jamie was accused of covering the costs of converting a tour bus into a food truck to help him sell the show.

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Furthermore, Britney Spears and Rosengart accused Jamie of "chronic alcohol abuse impairing his ability to serve faithfully."

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