A judge refused a request from the father of Britney Spears to exercise greater influence over her finances.
Since 2008, Jamie Spears has managed the financial affairs of his daughter, but the singer has recently suggested she wants him removed.
A judge upheld a previous decision on Thursday that made a financial firm a co-conservator for the artist.
The judge denied the request made by Mr Spears to retain his previous level of control over the investments of his daughter, reports the BBC.
The ruling means Mr Spears and the private trust firm, Bessemer Trust, will now have equal control to handle her finances.
As a result, in order to build a budget and investment plan for the singer's properties, he is now expected to collaborate with the company.
The conservatorship is a legal arrangement that was put in effect due to her mental health issues.
Los Angeles Judge Brenda Penny appointed Bessemer Trust as co-conservators in November, but rejected the star's effort to remove her father entirely.
Jamie Spears had objected to Bessemer's involvement, arguing that it reduced the power he has held for years. Judge Perry threw out his objection on Thursday. Another hearing is scheduled for 17 March.
Britney Spears' lawyer Samuel D Ingham III has previously said the singer is "afraid" of her father and does not want him to control her finances and career.
On Thursday, Mr Ingham reiterated the pop star's wish, adding that it was "no secret" she didn't want her father to be a co-conservator, but acknowledged that removing him altogether would be a "separate issue".
Interest in the case has been renewed after the recent release of a documentary that focuses on the conflict over the singer's guardianship.
Framing Britney Spears, which was produced by The New York Times, examined the conservatorship in depth, as well as how the singer has been treated by the media throughout her career.
It also explored the #FreeBritney movement, a campaign by some of the star's fans who believe her life and career are being controlled against her will. Campaigners from the group were outside the hearing on Thursday.
Babs Gray, host of the BritneyGram podcast, told the BBC outside the court: "It hasn't changed anything much today... I don't think a lot of forward movement will happen until Britney's lawyer actually files to get her out of the conservatorship."
She said interest in the #FreeBritney issue had "exploded" in the past week as a result of the documentary.
"It's been really encouraging to see how supportive everyone is about the movement, how they are reckoning with how Britney was treated in the past," she said. "I hope its not just a flash in the pan. I hope people keep paying attention and keep putting the pressure on."
Britney Spears hasn't performed live for more than two years, and insists she has no intention of doing so again until her father is forced to relinquish control over her career.