The feud between Britney Spears and her sister appears to be far from over after the popstar fired off a cease-and-desist letter ordering Jamie Lynn to stop talking about her in interviews to promote her new book.

Britney’s lawyer Matthew Rosengart claims that the “ill-timed” memoir, titled Things I Should Have Said, contains several “misleading or outrageous claims” and has accused Jamie Lynn, 30, of “exploiting” the Toxic hit-maker for “monetary gain”.

He does however admit that Britney, 40, has not (and will not) read the book.

“She will not tolerate it, nor should she,” the letter continued.

“Publicly airing false or fantastical grievances is wrong, especially when designed to sell books. It is also potentially unlawful and defamatory,” Rosengart warns in the letter.

“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,” it concluded.

Jamie Lynn has not yet publicly commented on the letter.

The sisters have been locked in a war of words on social media with Jamie Lynn recently calling for Britney’s team to take their issues offline and talk in person.

Britney has hit out at her younger sibling a number of times in social media posts, claiming that she was not supportive during her conservatorship, which finally came to an end after 13 years last November.

She has however stated that she loves Jamie Lynn “unconditionally”.