Britney Spears' father Jamie Spears has filed court papers which reveal the singer's co-conservator, who oversees the singer's health, is gravely concerned for Britney's mental state.

Britney Spears' dad has claimed he was recently told by her personal conservator that she was "mentally sick".

The 39-year-old singer has been under conservatorship since 2008, and while her father Jamie Spears currently oversees her estate and finances, Jodi Montgomery is in charge of her person.

Britney is pursuing legal action to try and have her father removed as co-conservator, but in new court documents filed by Jamie, it has been claimed Britney is in no fit mental state to make important decisions about her conservatorship.

Jamie alleged he received a phone call from a "very distraught" Jodi on July 9, who expressed her concerns to him regarding Britney's behaviour and overall mental health.

Britney's dad claims Jodi told him the Toxic hitmaker was "not timely or properly taking her medications, was not listening to the recommendations of her medical team, and refused to even see some of her doctors."

According to TMZ, Jamie says Jodi asked for his help, but he was unable to involve himself because he doesn't have access to Britney's medical information following his decision to step down as sole conservator.

Jamie is even claiming Jodi raised the possibility of placing Britney under a 5150 psychiatric hold, before backtracking on the request in an email sent on July 13.

Elsewhere in his documents, Jamie blasts Britney's new lawyer, Mathew Rosengart, and claims he has been making "vague accusations" about him.

The court filing added: "[Jamie's] sole motivation has been his unconditional love for his daughter and a fierce desire to protect her from those trying to take advantage of her."

Jamie is objecting to a request filed earlier this week by Britney's legal team, which would see the next court hearing in her conservatorship case moved forward from September to later this month.