Michael Avenatti, Ms Daniels' lawyer, says Americans "should be outraged". (Photo: AFP)

A California judge has ordered Stormy Daniels' lawyer Michael Avenatti to pay $4.85 million to an attorney at his former law firm.

The ruling was issued Monday in Los Angeles County Superior Court. Avenatti didn't attending the court proceeding.

The judge said Avenatti must pay the money because he personally guaranteed a settlement with Jason Frank in a lawsuit over back pay.

Frank alleged the firm misstated its profits and that he was owed millions.

Avenatti, who is toying with a possible 2020 presidential run, told The Associated Press that Frank owes him and the firm $12 million "for his fraud." He didn't provide details.

Monday's decision follows an earlier court ruling from a U.S. bankruptcy court judge who ordered Avenatti's former firm to pay $10 million to Frank.