The Washington Times reported Wednesday that the Illinois senator's new ad attacks Sen. Hillary Clinton, D-N.Y., who has accepted nearly $800,000 in campaign contributions from lobbyists.
"We can't end the Washington game ... until we change the players," the Web ad says.
The Obama campaign defended the ad, saying it offers a contrast, and is not a hit piece, the newspaper said.
Clinton spokesman Howard Wolfson said he would not respond to the ad unless the Obama campaign decided to put the Internet spot on the air.
"If it's something that they want to put their considerable resources behind by putting on television, we'll respond to it," he said.
Wolfson noted that Obama over the course of his political career has taken money from state lobbyists and political action committees.