LOS ANGELES (Reuters) - An attorney for Britney Spears on Monday asked a Los Angeles court to remove her father as conservator of her roughly $60 million estate following the pop singer's allegations that he had used the arrangement to mistreat her.

Mathew Rosengart, newly appointed as the performer's personal legal representative, requested in legal filings that the court replace Jamie Spears with certified public accountant Jason Rubin as the overseer of the singer's finances.

The matter will be discussed at a hearing in Los Angeles Superior Court scheduled for Sept. 29, Judge Brenda Penny said.

Britney Spears, 39, was placed under a conservatorship that controls her personal and financial affairs in 2008 after she suffered a mental health breakdown. The details of her mental health issues have never been revealed.

The "Stronger" singer recently told the court she wanted her father immediately removed and charged with conservatorship abuse.

In new court filings, Rosengart called the conservatorship a "Kafkaesque nightmare" that had grown "increasingly toxic and is simply no longer tenable."

He billed the proposed removal of Jamie Spears as an "initial narrow step" that might be followed by a bid to end the conservatorship entirely.

"There might well come a time when the Court will be called upon to consider whether the conservatorship should be terminated in its entirety," Rosengart's petition said.

Public support for Britney Spears has swelled since her emotional address to the court in June in which she called the conservatorship abusive and humiliating. Among her many claims, the singer said had been forced to perform and take medication against her wishes. A group of fans using the hashtag #FreeBritney has urged that all limitations imposed on her be removed.

An attorney for Jamie Spears did not immediately respond to a request for comment on Monday. He has said in previous statements and court filings that he loves his daughter and is looking out for her well-being. His lawyer, Vivian Thoreen, earlier this month said many of Spears' allegations were untrue.

Also on Monday, judge Penny agreed to a request that the parties have more time to discuss whether Britney Spears' estate will pay for around-the-clock security for Jodi Montgomery, who is the conservator of the singer's personal affairs. Montgomery has said she receives death threats due to her involvement in the case.

That issue also will be discussed on Sept. 29.

(Reporting by Lisa Richwine; Editing by Jonathan Oatis, Chris Reese and Sandra Maler)