The report from MAPlight.org, a non-partisan research group in Berkeley, Calif., said it found that in 2005-07, the average House member raised 79 percent of his or her campaign contributions from outside their district.

The report said the totals translated to $551 million in out-of-district contributions. In-district contributions totaled $146 million, or 21 percent. The remaining $3 million, or 0.5 percent, couldn't be pinned down, MAPlight.org said.

MAPlight.org also said in the report that of the top 20 most generous ZIP codes in terms of contributions, 15 were in the Washington area, home to scores of lobbyists and associations.

"We, as citizens, have handed special-interests the remote control, forcing our potential leaders to grovel before PAC leaders and lobbyists to raise the funds needed to win elections," MAPlight.org Executive Director Daniel Newman said in a written statement.

Newman claimed the cost of running a political campaign is so high that most lawmakers have to spend an inordinate amount of time schmoozing special interest groups when they should be representing the voters.