WASHINGTON – Embarrassed federal lawmakers are trying to rescind what they say is a mysterious provision passed over the weekend that appears to give some members of the House and Senate unrestricted ability to read the private tax returns of Americans.

Warning that the power could be used for “evil purposes,” Senator Schumer yesterday called for an investigation into how the provision was slipped into a $388 billion spending bill without debate or the blessing of congressional leaders.

Mr. Schumer said the bill would allow members of the Senate and House “to snoop and take a look at anyone’s IRS income tax returns, their political enemies’, their friends’, anyone they want,” and to use the information “for political, economic, evil purposes in any way.”

He called for punishment for the individual responsible for the language.

“This harkens back to the days of J. Edgar Hoover, when some unknown people could go and snoop on you, against the law, against the privacy that we all cherish,” Mr. Schumer said on CNN’s “Late Edition.”

The minority leader in the House, Rep. Nancy Pelosi, accused Republicans of perpetrating a “Saturday night massacre on the privacy of American taxpayers.”

Republicans also distanced themselves from the provision, which was buried in a piece of legislation passed over the weekend that combined nine separate spending bills into a single foot-high bill.

The chairman of the Senate Appropriations Committee, Senator Stevens of Alaska, apologized for the provision, which he said had been inserted without his knowledge.

The Senate approved a resolution to nullify the provision, and the House was expected to vote on a similar measure as early as Wednesday. The legislation will not be given to the president to sign until the resolution passes.

The majority leader in the Senate, Senator Frist, said he had “no earthly idea how that got in there.” No one would defend the provision, he said on CBS’s “Face the Nation.”

Other Republicans said they were equally baffled.

“Something happened clearly in the dark of night. …The Senate was totally amazed,” said Senator Hutchison, a Republican of Texas, speaking on “Late Edition.”

The bill would give the chairmen and staff members of the House and Senate appropriations committees access to federal tax returns, notwithstanding other laws that govern the release of tax information.The provision amounts to an exemption for congressmen and their staff from civil and criminal penalties, including fines and up to five years in prison, for disclosing the information to unauthorized people, said the senior Democrat on the Senate Finance Committee, Senator Baucus of Montana.

Under current law, members can see tax returns with special permission from the committee chairmen, and they are subject to strict privacy rules that were enacted in response to the Watergate scandal and President Nixon’s attempts to use the IRS to go after those on his enemies list, Mr. Baucus said in a statement.

In addition to disclosing a person’s earnings, tax forms can include person al information about mental disability, adoption, gambling losses, unemployment benefits, medical expenses, and donations to organizations, he noted.

“Such an eleventh-hour grab for access to tax returns is a dangerous precedent that seriously threatens our voluntary tax system,” Mr. Baucus said in a statement.

Dr. Frist was quoted by the Associated Press linking the provision to the chairman of the House Transportation and Treasury Appropriations Subcommittee, Rep. Ernest Istook, a Republican of Oklahoma.

Mr. Istook reportedly said in a statement that the Internal Revenue Service drafted the language, which would not have allowed any inspections of tax returns. “Nobody’s privacy was ever jeopardized,” the AP quoted the statement as saying.

A spokeswoman for Mr. Istook did not return requests for comment yesterday.

Suspicions also centered on House Republicans’ staffers who had access to the bill in a painstaking marathon process of putting together nine separate spending bills into one massive omnibus bill.

If a staffer was responsible for inserting the language,he or she would be expected to be fired, said one Democratic congressional aide.

“It’s a pretty serious breach. Staff members do a lot of the work, but we are not elected by anybody and we don’t vote on anything. That’s not our job,” the aide said.

Senator McCain of Arizona said the fact that the provision got into the bill is evidence of a legislative system that is “broken.”

“How many other provisions didn’t we find in that 1,000-page bill?” he asked on NBC’s “Meet the Press.”