Richard Cullen said the investigation into DeLay's alleged ties to convicted GOP lobbyist Jack Abramoff was officially ended last week, The Hill reported Monday.
"The federal investigation of Tom DeLay is over, and there will be no charges," Politico.com quoted Cullen as saying. "This was one of the longest and expensive and thorough investigations in recent memory. DeLay took a tack right from the start that he had nothing to hide, and we have been in a routine and constant dialogue with (prosecutors)."
Abramoff went to prison in 2006 on numerous corruption convictions.
The Campaign for Fair Elections, a non-partisan watchdog group, denounced the Justice Department decision.
"The decision by the Department of Justice to drop its criminal investigation into former Majority Leader Tom DeLay's relationship with convicted lobbyist Jack Abramoff is further evidence that the scandal is not what is illegal, but rather what is legally permitted each and every day in Washington, D.C.," the group's campaign manager, David Donnelly, said in a statement.
DeLay still faces criminal charges in Texas for alleged illegal political contributions in the 2002 state elections. A hearing in that case is scheduled for Aug. 24, and a trial could begin in the fall, The Hill said.
Delay started a consulting firm, First Principles LLC, when he left office.