Britney Spears is launching yet another attack against Jamie Lynn Spears. She calls her a selfish brat despite having sent a cease and desist letter to her younger sister requesting that she stop talking about Jamie Lynn Spears.

Yesterday, Mathew S. Rosengart, the attorney for Toxic singers claimed his client would “go high” and abstain from further comments in their feud. But Britney is now doubling down on family disputes.

Britney deleted her Tuesday post, where Britney (40) said that she should have slapped Jamie Lynn (30, and Lynne Spears (30), respectively. Britney has since re-posted a longer version on Wednesday with additional details.   

Britney refers to Jamie Lynn as a “selfish brat” who refused to play after Justin Timberlake split with her. 

Toxic: Britney Spears has posted yet another blistering attack on Jamie Lynn Spears, calling her a 'selfish brat,' despite sending a cease-and-desist letter ordering her younger sister to stop talking about her

Toxic: Britney Spears has posted yet another blistering attack on Jamie Lynn Spears, calling her a ‘selfish brat,’ despite sending a cease-and-desist letter ordering her younger sister to stop talking about her

Britney was 21 years old at the time. Jamie Lynn, her younger sister, would have turned 11 in that same year.  

‘You selfish little brat !!!’ Britney covers her eyes with notes. Britney fumes in her notes. She was so proud and you told that interview girl that it was just weird … LIKE I GUESS I WILL JUST WALK IN THESE HALLS … Why did you say that ???’

She also continues to deny Jamie Lynn’s accusation that she once ‘grabbed a knife’ and locked them in a room together, which was shared in a recent interview on ABC’s Nightline. 

Britney wrote: “And the subject about the knife, which ironically is the only lie that you have ever told in all your life… Why is this conversation lasting 20 minutes? and the most degrading to me … OH BUT you don’t want to keep talking about it because you don’t want to HURT ANYBODY’S feelings … yet you let it linger forever saying you felt unsafe with me and WEIRD … f**k you Jamie Lynn !!!!’  

Longer version of events: Britney Spears goes on ANOTHER foul-mouthed rant against sister Jamie Lynn on Wednesday... despite issuing her with a cease-and-desist letter the day before

Longer version of events: Britney Spears goes on ANOTHER foul-mouthed rant against sister Jamie Lynn on Wednesday… despite issuing her with a cease-and-desist letter the day before

In her long post, the pop singer shows a broken relationship and suggests that Jamie Lynn was more fortunate than she. 

Britney says that Britney was not interested in playing with her younger sister when she was ten years old. Britney said Jamie Lynn did her hair just like Christina Aguilera. 

“You and your small friends believed I was uncool when I arrived home…. They felt bad about me during the breakup…. HELL NO, they didn’t! Your friends dyed you hair Christina Aguilera-style and no longer wanted to play with me !!!’ 

Britney’s legal team directed Jamie Lynn to cease discussing Britney’s personal life and struggles while she was giving interviews in support of her book.

Jamie Lynn currently is in promotion for her new book, ‘Things You Should Have Said. Britney’s legal counselor stated that it contains “misleading or outrageous claims” about Jamie Lynn. 

Britney Spears (pictured) yesterday sent a cease-and-desist letter ordering her sister, Jamie Lynn Spears, to stop talking about her.

Britney Spears (pictured), yesterday wrote a cease and desist letter to Jamie Lynn Spears requesting that she stop talking about Britney.

Jamie Lynn is currently on a promotional tour for her new book 'Things I Should Have Said', which Britney's legal counsel said contains 'misleading and outrageous claims' about Britney

Jamie Lynn is on a promotion tour for her book, “Things I Should have Said”. Britney’s legal counsel stated that the book contains misleading and outlandish claims about Britney.

Lawyer Mathew Rosengart has written a stinging letter to Jamie Lynn, demanding that she 'cease and desist from referencing Britney derogatorily' and threatening 'all appropriate legal action' should the actress not comply

Mathew Rosengart, an attorney, wrote a bitter letter to Jamie Lynn asking her to stop referring to Britney in derogatory terms and threating legal action against the actress if she doesn’t.

Mathew Rosengart, the lawyer for Jamie Lynn wrote an angry letter requesting that Jamie Lynn ‘cease from referencing Britney derogatorily’ and threatened ‘all appropriate legal actions’ against her if she didn’t. 

“We wrote with some hesitation, because Britney doesn’t want to draw more attention to her ill-timed book, its misleading, or outrageous claims about herself,” the letter was read exclusively by Page Six.

Britney did not read or intend to read your book. However, millions of Britney’s fans were surprised to discover how you had exploited Britney to make monetary gains. It is unacceptable and she should not be able to tolerate it.

The letter comes as Britney hit out against Jamie Lynn and her mother Lynne in a fiery Instagram post in which she said she should have slapped them both ‘across their f***ing faces’.

Lawyer Mathew Rosengart has written a stinging letter to Jamie Lynn, demanding that she 'cease and desist from referencing Britney derogatorily' and threatening 'all appropriate legal action' should the actress not comply

Mathew Rosengart, an attorney, wrote a bitter letter to Jamie Lynn asking her to stop referring to Britney in derogatory terms and threating legal action against the actress if she doesn’t.

Pictured: the cover of Jamie Lynn Spears' memoir, entitled Things I Should Have Said. Britney Spears' lawyers have claimed the 'ill-timed book' contains 'misleading or outrageous claims about her'

Photo: Jamie Lynn Spears’ book, Things I Should Not Have Said. Britney Spears lawyers claim that the book is ill-timed and contains “misleading claims or outlandish statements about her”.

Britney was raised under Jamie Spears’ conservatorship for many years. However, Rosengart stated that Britney would not be ‘bullied by’ anyone anymore.

It continued, “You, of all people, know the abuse Britney endured during the conservatorship after growing up with an alcoholic father. 

“In reality, your book states that your father “spent the majority of his life in this cycle of ruinous behavior.” He drank excessively, causing me torment and sadness.

Britney won’t be bullied or manipulated by her father, nor anyone else, after she was subject to a 13 year conservatorship.

Jamie Lynn was charged with ‘airing fake or fantastical grievances to gain publicity for her book’. She warned her sister that she will pursue further legal action against her sister if they continue to talk about their relationship.

Page Six received the letter for the first time. It stated that Britney was the breadwinner of her family and also supported you in other ways. Publicly expressing fantasical or false grievances, especially when you are trying to sell books, is wrong. This is illegal and potentially defamatory.

Michelle Obama said it best: “When they get low, we get high.” Britney, to her credit, is doing exactly that, at least for now.

Stolen glory: She seemed to intimate that her successful music career and reputation was the reason her sister was added to the main cast of Nickelodeon's All That in 2002

Stolen glory

“You stated recently that the book wasn’t about her. You are taking Britney at your word. We demand you stop referring to Britney in derogatory terms during your promotion campaign.

Britney will take appropriate legal action if you fail to follow through or insult her.

News of the letter comes as Britney continues to hit out at her sister and mother in a wild Instagram post in which she said she should have ‘slapped’ her family members ‘across your f***ing faces.’ 

Britney suggests that Jamie Lynn had been raised with a lot of care and had taken a leading role in TV shows as a child.

Lynne Spears also lashed out at her mother for not supporting her following her separation from Justin Timberlake.

Jamie Lynn’s sources told TMZ they were ‘disturbed by’ the Instagram video and feared for their safety. Jamie Lynn claims Britney feels ‘immense jealousy’ over Britney’s childhood.

According to the source Jamie Lynn receives death threats “every time Britney posts”, and Britney has repeatedly asked Jamie Lynn to cease.

Britney Spears (L) and Jamie Lynn Spears (R) during Nickelodeon's 16th Annual Kids' Choice Awards at the Barker Hangar April 12, 2003, in Santa Monica, California

Britney Spears (L, Jamie Lynn Spears) during Nickelodeon 16th Annual Kids’ Choice Awards at Barker Hangar on April 12, 2003 in Santa Monica, California

Britney posted a stock image of sweet holiday beverages in her last post. This seemed to be an attack on her sister who was drinking similar drinks.

Her sister recalled sitting at home, enjoying an easy lifestyle after her split from Timberlake. However, her mother wasn’t able to provide support for her since she was taking too much medication.

She said that Timberlake was her only family and that it was shocking that this had happened to her. 

‘I flew home to Jamie Lynn on the couch watching her tv shows right after Justin and I broke up… I was a ghost there!!!!!’ She wrote. ‘I had worked my whole life and I didn’t know how to be served by Mamma … Sit there and get served the chocolate milkshakes with the perfectly crushed ice with the secret chunky sugar meanwhile Jamie Lynn is 12, she indulges with the TV for hours then goes to lay out on a raft at the pool.

“My Mamma had to be on pain medication. She couldn’t hold a conversation because she and my father split. According to her, she claimed. ‘I remember her sitting on the floor in a conversation and she never got up…’