The Massachusetts Democratic Party filed an ethics complaint against Republican US Senator Scott Brown just hours before he was due to debate his Democratic challenger Elizabeth Warren Wednesday night, claiming he has violated ethics law by failing to divulge a complete list of the clients for whom he has done legal work.

They allege in the complaint that Brown was required to disclose any sources of compensation over $5,000. His 2009 candidate report, they say, showed income from his law practice, but did not list specific clients.