A source with knowledge of the situation confirmed the news to CNN.
Rudolph's letter of resignation was sent to Spears' father Jamie Spears and to the conservator of her person, Jodi Montgomery.
"It has been over 2 1/2 years since Britney and I last communicated, at which time she informed me she wanted to take an indefinite work hiatus," Rudolph wrote in the letter first obtained by Deadline. "Earlier today, I became aware that Britney had been voicing her intention to officially retire."
CNN has reached out to Spears' publicist for comment on her potential plans to make her work hiatus permanent.
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The letter went on to say, "As you know, I have never been a part of the conservatorship nor its operations, so I am not privy to many of these details. I was originally hired at Britney's request to help manage and assist her with her career. And as her manager, I believe it is in Britney's best interest for me to resign from her team as my professional services are no longer needed.
"Please accept this letter as my formal resignation
"I will always be incredibly proud of what we accomplished over our 25 years together. I wish Britney all the health and happiness in the world, and I'll be there for her if she ever needs me again, just as I always have been."
Rudolph began working with the singer in 1995. A rise to global fame followed for Spears with her breakout smash, "Baby One More Time" in 1998. Rudolph has also managed other artists, including Miley Cyrus, Toni Braxton and Justin Timberlake.
The news comes after Spears' bombshell hearing on June 23 in which she called her nearly 13-year conservatorship "abusive." She went on to claim that she had been forced to perform and take medication against her will.
The next court hearing is scheduled for July 14.
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Britney Spears' court-appointed attorney resigns
Britney Spears' court-appointed attorney on Tuesday filed documents to resign from her conservatorship, the latest of several such moves that have come in the fallout from the pop singer's comments in court decrying the legal arrangement that controls her money and affairs.
Samuel Ingham III filed documents in Los Angeles Superior Court requesting that the court appoint Spears a new attorney, and saying his resignation would take effect as soon as that happened.
During her June 23 speech in court, in which she condemned the conservatorship and asked Judge Brenda Penny to end it, Spears was critical of Ingham, and said she wished the court would allow her to hire a lawyer of her choice.
Last week, Bessemer Trust, the estate-management company that Spears had requested replace her father as conservator of her finances, filed its own documents withdrawing from the case. The filing said that circumstances had changed after Spears' comments in court on June 23.
At a hearing in November, Penny denied Spears' request to have her father replaced entirely, but said James Spears and Bessemer Trust could work together as co-conservators of her finances.
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A veteran probate attorney, Ingham was for years a largely silent figure in the conservatorship, at least publicly, but became a more vocal advocate for Britney Spears starting last year. His statements in court that she feared her father and would not resume her career so long as he had power over it were an early crack in the presumed consensus among the figures involved in the conservatorship.
At the June 23 hearing, Ingham said that Britney Spears had not asked him to file a petition to end the conservatorship, but said he expected she might do so soon. In her remarks critical of Ingham, Spears said during the hearing that she hadn't known she could file such a petition, and she still has not.
The Associated Press contributed to this article.