Michael Jackson's mother will challenge the trusteeship of his estate in court because she believes financial handlers have been fleecing the pop icon for the last 20 years, says the author of a book on the singer's final days.

Biographer Ian Halperin cited unidentified sources in Jackson's family and the Los Angeles Police Department as he described that development at a news conference on Monday.

Katherine Jackson's lawyer, L. Londell McMillan, has asserted that she should given "a seat at the table" in executing deals for the estate, powers that are now exclusive to the special administrators.

He has also said there could be a conflict of interest that could compromise co-executors John Branca and John McClain.

"Katherine Jackson is contesting officially Branca and McClain as being executors of Michael Jackson's will," Halperin said, adding that he had confirmation that at the time of Michael Jackson's death Branca and McClain "were not his choice to run his estate."

The author said he has learned that Katherine Jackson accused some of her son's handlers of fraudulent practices over a 20-year-plus period.

Halperin also announced that a celebrity judge is offering to mediate the custody battle over Jackson's children.

Larry Seidlin, the former Florida judge who adjudicated the infamous Anna Nicole Smith body custody case, is offering his services to the Jacksons.

Halperin, a Montreal native, has written a book on Jackson's final days.