An investigative report by The Atlanta Journal-Constitution found that the two Georgia insurance companies sent the money into Oxendine's campaign through 10 Alabama-based political action committees.
Georgia law forbids public officials from taking money from the companies they regulate.
Oxendine said in a statement that he had requested an advisory opinion from the state ethics officials days before the newspaper's story ran on Sunday. He called the story a "hit piece."
The political action committees were formed by Donald V. Watkins, a director of Admiral Life Insurance Co. of America and State Mutual Insurance. Both firms are headed by Delos "Dee" Yancey III from the same building in Rome, Ga.