Los Angeles, California – Britney Spears has at last petitioned the court to appoint a successor to the conservatorship of her estate, calling her father's broad control of her career and fortune "traumatizing, insane, and depressing" in new legal documents filed Monday.

The documents, filed in Los Angeles Superior Court by the pop star's newly appointed personal attorney – former federal prosecutor Mathew Rosengart – made good on his promise to move "aggressively and expeditiously" to relieve her father James "Jamie" Spears of his duties involving the 39-year-old singer's life and finances.

The 20-page petition asked the court to replace Jamie Spears with another fiduciary, interim conservator, certified public accountant Jason Rubin – a "licensed professional fiduciary whose presence is not detrimental to Ms. Spears's well-being," it said.

Earlier this month, Bessemer Trust, cited as co-conservator of Spears' estate since November, resigned from the job it apparently never started.

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The petition described the relationship between Spears and her father as "venomous" and alleged that "it impairs Ms Spears's mental health, her well-being, and her ability to pursue and continue with her extraordinary career."

It's the latest in the hitmaker's protracted court battle that has illuminated her fraught relationship with her father and conservatorship issues as a whole.

The arrangement came to a dramatic climax in late June, when the singer addressed the court and essentially torched the state of the conservatorship and almost everyone involved in it.

In Monday's petition, Rosengart argued repeatedly that the purpose of the conservatorship is to fight to protect the conservatee's interests rather than gain control over the conservatee, which critics of the arrangement have long believed the elder Spears has done.

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Rosengart replaced court-appointed attorney Samuel Ingham III and the firm Loeb & Loeb, both of whom had recently tendered their resignations pending assignment of new representation.

Describing it as a "Kafkaesque nightmare," Rosengart said that the conservatorship, at least when it comes to Jamie Spears, "has grown increasingly toxic and is simply no longer tenable." The petition asks him to resign voluntarily, or at least not oppose the petition for his removal.

Representatives for Jamie Spears' attorney did not immediately respond to a request for comment on Monday evening.

Rosengart also argued that Jamie Spears profited handsomely from his daughter's conservatorship, noting that since at least 2009, he has been paying himself $16,000 per month from the singer estate, which is $2,000 more than he has allotted to his daughter.

He also pays himself an additional $2,000 per month for office expenses. Rosengart also noted that the elder Spears is not a professional business or financial manager, and that the family has struggled financially under his leadership and filed for bankruptcy in 1998.

"Regardless of whether Mr Spears resigns voluntarily (as he should do immediately), this court should remove and replace Mr Spears for these very reasons," he said in Monday's petition.

Rosengart also has the backing of Jodi Montgomery, the conservator of Britney Spears' person, and her mother, Lynne Spears.

The newly filed petition also said that Spears may have needed the legal arrangement when it was first initiated 13 years ago, but that her circumstances have since changed.

Rosengart reiterated that their father-daughter relationship is "so fractured" that she and her father "do not even speak" and that any interaction between the singer and her dad is "unwelcomed and needlessly stressful for Ms Spears, who...has testified that she is fearful of her father, along with many reasons for that fear."

Monday's hearing appeared to be set to finalize a request made by Montgomery to be compensated for her heightened security. Since the explosive June hearing, Montgomery said "the amount as well as the severity of the threats has drastically increased," threatening her safety. A July 19 hearing was held regarding the petition, but lawyers asked for more time to discuss Montgomery's security issue.

Montgomery has been conservator of Spears' person since September 2019 and sees to her personal affairs. The temporary appointment has been extended through October 8, according to a petition also filed Monday.

A hearing scheduled on September 29 is supposed to deal with many of the accounting issues that have been delayed for months.

Earlier this month, Spears called for the immediate removal of her father from the conservatorship and accused him of conservatorship abuse, including having been forced into a mental health facility against her will as punishment for standing up for herself.

She also demanded that the protracted legal arrangement be terminated altogether, but not if it required going through more "stupid" evaluations questioning her intelligence. Spears described being denied things as basic as coffee, her driver's license, and her "hair vitamins" by the conservatorship.

But the singer has reportedly pushed for her father's removal for years, according to a report in the New York Times, which cited confidential court records and shed light on past closed-court proceedings from the pop star's point of view.

Spears questioned her father's fitness for his duties as early as 2014, in a hearing closed to the public, the newspaper said, and expressed serious opposition to the conservatorship earlier and more often than had previously been known.