Several voter rights advocacy groups say the state of Missouri is not following federal requirements on providing voter registrations.
The League of Women Voters of Missouri and four other groups sent a letter Thursday to Missouri Secretary of State Jay Ashcroft and to Joel Waters, director of the state Department of Revenue.
They contend the state doesn't automatically update voter registrations when people change the address on their driver's licenses or state ID. They also say the state requires unnecessary duplication of information, whether the change is made online, by mail or at state offices.
The groups say if Missouri doesn't correct its practices in 90 days, they are prepared to take legal action.
A spokeswoman for Ashcroft's office did not immediately return a call seeking comment.