The Toxic hitmaker has been fighting to end Jamie Spears' role as sole conservator of her estate for months, recently suggesting he should work alongside officials at financial management organisation the Bessemer Trust Company, giving them the power of attorney to control her affairs.

As part of her legal challenge, she is asking the judge to unseal a number of documents, including those regarding her medical records, making them available for public view - a move Jamie insists should remain private for the sake of Britney and her two sons.

Now he is asking court officials to determine that the singer has "the capacity to understand the consequences of her waiver" to keep her files under wraps, reports TMZ.

Jamie also notes the conservatorship, which has been in place since 2008, following Britney's much-publicised breakdown, is voluntary, and until now, she has not requested for it to be terminated.

He explains the finances of his daughter's estate are "inextricably entwined" with the personal aspects of her conservatorship, and making certain documents public could expose sensitive medical information.

His latest filing comes days after Britney's lawyer issued a statement denying there was anything to protect from the public.

"Britney argues there are no medical issues or sensitive issues with her children to protect, so there's no reason to keep the hearing secret," the lawyer explained. "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."