Washington ? Five conservative nonprofit organizations, including one run by prominent Republican Grover Norquist, “perpetrated a fraud” on taxpayers by selling their clout to lobbyist Jack Abramoff, Senate investigators said in a report issued Thursday.

The report includes previously unreleased e-mails between the now-disgraced lobbyist and officers of the nonprofit groups, showing that Abramoff funneled money from his clients to the groups. In exchange the groups, among other things, produced ostensibly independent newspaper op-ed columns or news releases that favored the clients’ positions.

Officers of the groups “were generally available to carry out Mr. Abramoff’s requests for help with his clients in exchange for cash payments,” said the report, issued by the Senate Finance Committee. The report was written by the Democratic staff after a yearlong investigation and authorized by the Republican chairman, Sen. Charles Grassley, R-Iowa.

Abramoff has pleaded guilty to fraud and conspiracy and could go to prison as early as next month. The investigation has resulted in one conviction and seven guilty pleas, including from one lawmaker, Rep. Robert Ney, R-Ohio, who is to appear today before a federal judge in Washington, D.C.

The report bolstered earlier revelations that Abramoff laundered money through the nonprofits to pay for congressional trips and paid Norquist to arrange meetings for his clients with government officials, including White House senior adviser Karl Rove.

The groups named in the report are Norquist’s Americans for Tax Reform; the Council of Republicans for Environmental Advocacy, which was co-founded by Norquist and Gale Norton before she became Secretary of the Interior; Citizens Against Government Waste; the National Center for Public Policy Research, which was a spinoff of the Heritage Foundation; and Toward Tradition, a Seattle-based religious group founded by Rabbi Daniel Lapin.