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 routed 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 Democratic members of the Senate Finance Committee after a one-year investigation.

Abramoff has pleaded guilty to fraud and conspiracy and is cooperating with federal investigators in the ongoing influence-peddling probe that has resulted in seven guilty pleas and convictions.

The report states that the groups probably violated their tax-exempt status "by laundering payments and then disbursing funds at Mr. Abramoff's direction; taking payments in exchange or writing newspaper columns or press releases that put Mr. Abramoff's clients in a favorable light; . . . and agreeing to act as a front organization for congressional trips paid for by Mr. Abramoff's clients."

The groups 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 religious group founded by Abramoff friend Rabbi Daniel Lapin.

E-mails released by the committee show that Abramoff routinely used the groups for his lobbying activities. Often with the knowledge of the groups' leaders, Abramoff exploited the tax-exempt status and leveraged the stature of the organizations to build support among conservatives for legislation or government action sought by his corporate clients.

Sen. Max Baucus, D-Mont., the ranking Democrat on the committee, said the Internal Revenue Service and FBI should investigate the groups.

"These groups' dealings with Jack Abramoff certainly violated the spirit, and perhaps the letter, of the laws that give charitable and social welfare organizations a break for the good work they're supposed to do," Baucus said in a statement.

Though the report was issued by Democrats on the Senate Finance Committee, Chairman Charles Grassley, R-Iowa, endorsed its findings. An aide to Grassley said the senator did not co-author the report because he had hoped it would have included Democratic groups that he believes also breached their tax status.

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