The pop singer, 38, has had her affairs overseen by her father, James Spears, since 2008, when she endured a public unravelling.
Mr Spears wants to keep parts of the case sealed, but Britney’s lawyer argues it is in both hers and the public’s interest to open it to scrutiny.
The star is “vehemently opposed to this effort by her father to keep her legal struggle hidden away in the closet as a family secret”, a new filing at a Los Angeles court states.
And Britney’s lawyer Samuel D Ingham III appeared to endorse the #FreeBritney movement, a viral campaign Mr Spears reportedly dismissed as a conspiracy theory.
A filing lodged at court in Los Angeles said: “Britney’s conservatorship has attracted an unprecedented level of scrutiny from mainstream media and social media alike.
“Far from being a conspiracy theory or a ‘joke’ as James reportedly told the media, in large part this scrutiny is a reasonable and even predictable result of James’ aggressive use of the sealing procedure over the years to minimise the amount of meaningful information made available to the public.”
Mr Spears and his lawyers have routinely sought to have legal filings sealed from the public and hearings held behind closed doors, requests which have often been granted by the court.
Mr Ingham said those tactics may have had “merits” when Spears was trying to restart her career, however “at this point in her life when she is trying to regain some measure of personal autonomy, Britney welcomes and appreciates the informed support of her many fans”.
He added: “Although the sealing motion is supposedly for her ‘protection,’ Britney herself is vehemently opposed to this effort by her father to keep her legal struggle hidden away in the closet as a family secret.”
The #FreeBritney movement often holds protests outside the Los Angeles Superior Court during hearings for the case. They have called for an investigation into the conservatorship.
Celebrities including Miley Cyrus, Ariel Winter, Ruby Rose and Paris Hilton have also signalled support for the movement.
Mr Spears and lawyer Andrew M Wallet were Britney’s co-conservators until the latter stepped down in 2019. Mr Spears temporarily stepped down from conservator of his daughter’s personal affairs last year, but retained control of her finances.
Jodi Montgomery then became conservator of Britney’s personal affairs. In legal papers lodged last month, Britney said she wanted Montgomery to stay in the role and strongly objected to her father returning.
The conservatorship also holds influence over her relationship with her two teenage sons. Spears’ ex-husband Kevin Federline has custody of the boys, but she has frequent visits with them.
Once one of the world’s biggest pop stars, Spears last performed live in October 2018, before cancelling a much-anticipated Las Vegas residency in early 2019.
