He added: "It makes me wonder where the allegiance lies. Is the conservator making decisions in the best interest of the conservatee or the business manager who they owe a debt to?"
Taylor's lawyer, Charles Harder, insisted Jamie repaid the loan and denied it had any impact on Tri Star's work with the conservatorship.
He said in an email: "A small loan, later repaid, had no affect on Tri Star's work for the estate in later years."
Earlier this month, Jamie filed a formal complaint against the Circus hitmaker and her team in Los Angeles Superior Court.
The 69-year-old patriarch claimed he wanted to tie up loose ends and move on after Britney's conservatorship was officially dissolved, but blasted the 40-year-old singer's "temporary conservators" for dragging out the process.
He also accused Britney and her team of releasing "statements with no other purpose than to attack" him and trying to depict him as a "disgraced, suspended conservator".