Britney Spears is fighting the ruling that gives her father complete control of her estate and affairs until July.
The singerís lawyer, Jon Eardley, is claiming that the conservatorship was granted without the necessary five days notice, and so is invalid, reports BBC News.
In early February, a California state court granted temporary conservatorship to James Spears until July, when the order will presumably be reviewed.
However, there is also some doubt as to whether Eardley can legitimately represent Spears as, under the rules of the conservatorship, the singer is unable to appoint her own legal personnel without the involvement of her father or his lawyer.
Spears has been in constant court battles since early January, when she refused to return her two children to ex-husband Kevin Federline.
The stand-off resulted in two stays in a psychiatric hospital for Spears.