Speaking to Radar Online, Michael said he questioned Holley's ethics.
"While I thought Shawn did a great job defending Lindsay in court ethically, she did a horrible job morally," he said.
Michael added: “I can't tell you how many times Shawn told me in person and over the phone that she thought Lindsay needed to be in rehab, and then she would turn around and say she had to do what Lindsay told her to do because she was her lawyer.
"To me, that crosses a moral boundary."
Earlier this week, Judge Marsha Revel ruled that Lohan must spend 90 days in prison for violating the terms of her probation in relation to a 2007 DUI charge.
Michael claims that Shawn had convinced Lohan during the court date that she would not receive any jail time.