Britney Spears' New Lawyer Moving 'Aggressively' to Remove Jamie Spears from Conservatorship

Britney Spears' new lawyer, Mathew Rosengart, is wasting no time as he joins the pop star's ongoing conservatorship battle.

Speaking to reporters on Monday, Rosengart — whose firm has represented celebrities including Steven Spielberg, Sean Penn, Ben Affleck and Eddie Vedder — said that he is working "aggressively" and "expeditiously" to remove Britney's father Jamie Spears from her conservatorship.

"First, I once again want to thank Britney Spears for her courage and for her strength," Rosengart said in video footage shared on Twitter. "I want to thank Judge [Brenda] Penny for her courtesy welcoming my firm and I into this case. And I also want to thank Britney Spears' fans and supporters. The outreach and support for my firm, myself, and most importantly, Britney, has truly been overwhelming."

"Finally, and the last thing I'm going to say about this matter, is as I said in court last week, and outside, my firm and I are moving aggressively and expeditiously to file a petition to remove Jamie Spears unless he resigns first."

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RELATED: Britney Spears' 'Main Goal' After Hiring New Lawyer Is to Have Dad Jamie Removed as Conservator: Source

Britney's "main goal" after hiring Rosengart, a source told PEOPLE last week, is to see her father Jamie removed as the conservator of her estate.

"She's really happy and excited that she has new representation," the source said. "She feels like she's finally heading towards ending this."

Rosengart is also expected to ask the court to forgo a mental health evaluation for Britney, who "doesn't have much trust for the doctors that she has worked with so far," a source told PEOPLE earlier this month.

Jamie, 69, stepped down as his daughter's personal conservator in late 2019, but remains in charge of Britney's finances after fiduciary company Bessemer Trust resigned as co-conservator of her estate.

getty Britney Spears

RELATED: Britney Spears Says She Wants to Charge Dad Jamie with 'Conservatorship Abuse' in New Testimony

Britney spoke publicly about the 13-year conservatorship for the first time in an impassioned speech to the court on June 23. The singer's personal conservator Jodi Montgomery and Jamie have been sparring publicly in the weeks since.

A filing submitted by Jamie at the end of June blamed Montgomery for the "difficulties and suffering" Britney described in court. Montgomery responded with a statement from her lawyer saying that she has been a "tireless advocate" for Britney.

Britney reportedly told Judge Penny in court last week that she is "extremely scared" of Jamie. "This conservatorship has allowed my dad to ruin my life," she said, NBC News reported. The outlet added she said she wants to charge her dad with "conservatorship abuse."