Barack Obama's campaign is rejecting claims of any ties to a community activist group that registers voters.

The group, known as ACORN, is reportedly being investigated by the FBI. Sources say the bureau is looking into whether ACORN helped foster voter registration fraud around the nation before the presidential election.

An attorney for the Obama campaign, Robert Bauer, says ACORN is not an "agent" for the campaign, nor has it performed registration services for the campaign.

In a letter to Attorney General Michael Mukasey, Bauer asks that any investigation into registration irregularities be turned over to a special prosecutor currently investigating partisan political firings of U.S. attorneys.

Vice presidential candidate Sarah Palin today kept up the Republican ticket's attack on ACORN, saying Obama hasn't been forthcoming about his ties to the group.