WASHINGTON, Dec. 20 - The limited oral briefings provided by the White House to a handful of lawmakers about the domestic eavesdropping program may not have fulfilled a legal requirement under the National Security Act that calls for such reports to be in written form, Congressional officials from both parties said on Tuesday.

The White House has refused to describe the timing and scope of the briefings, except to say that there were more than a dozen. But among the small group of current and former Congressional leaders who have attended the high-level gatherings conducted by Vice President Dick Cheney at the White House, several have described them as sessions in which aides were barred and note-taking was prohibited.

All told, no more than 14 members of Congress have been briefed about the program since it took effect in 2001, the Congressional officials said. Now lawmakers from both parties are debating whether those members-only briefings provided a sufficient basis for oversight of an activity that is only now coming under intense Congressional scrutiny.

"You can't have the administration and a select number of members alter the law," Senator Arlen Specter, the Pennsylvania Republican who heads the Judiciary Committee, said this week. "It can't be done."

Senator Harry Reid, Democrat of Nevada, said this week that he had received only a "single, very short briefing" on the subject this year, after taking over as his party's leader. Mr. Reid has called on Congress to review not only whether the program was authorized, but also what he called a "flawed Congressional consultation system" in which the White House maintained the upper hand.

Without a written record or the recollections of staff members to guide them, members of Congress who have attended the briefings have provided starkly different versions of what they were told at the sessions, which they said were almost invariably led by Mr. Cheney and Gen. Michael V. Hayden, who as director of the National Security Agency oversaw the effort.

"When I was briefed on it, you couldn't help but conclude that it would have an impact on Americans," said Representative Peter Hoekstra, Republican of Michigan, the chairman of the House Intelligence Committee.

Mr. Hoekstra said that he was first summoned to one of the sessions in August 2004, after taking over as panel chairman, and that he had attended two others since, with the other leaders of the House and Senate Intelligence Committees.

But Bob Graham, a former Democratic senator from Florida who was chairman of the Intelligence Committee, said his recollection from an initial briefing in late 2001 or early 2002 was that there had been no specific discussion that the program would involve eavesdropping on American citizens.

"You don't know what you don't know," Mr. Graham said, adding that he would have objected to the program had he been fully briefed on its dimensions.

Among Democrats, both Senator John D. Rockefeller IV of West Virginia, the senior Democrat on the Senate Intelligence Committee, and Representative Nancy Pelosi of California, the House Democratic leader, have said in recent days that they raised objections to the program in classified letters after first hearing about it. Mr. Rockefeller did so in July 2003, after he was first briefed about the eavesdropping effort; Ms. Pelosi has not identified the date of her objections, saying her letter remains classified.

But neither lawmaker sought to block the program legislatively, an option that Republicans who have sought to rebut the Democrats' complaints have said might well have been pursued.

"A United States senator has significant tools with which to wield power and influence over the executive branch," Senator Pat Roberts, the Kansas Republican who heads the Senate Intelligence Committee, said on Tuesday. "Feigning helplessness is not one of those tools."

The demand for written reports was added to the National Security Act of 1947 by Congress in 2001, as part of an effort to compel the executive branch to provide more specificity and clarity in its briefings about continuing activities. President Bush signed the measure into law on Dec. 28, 2001, but only after raising an objection to the new provision, with the stipulation that he would interpret it "in a manner consistent with the president's constitutional authority" to withhold information for national-security or foreign-policy reasons.

A White House spokesman declined on Tuesday to say whether the administration had ever provided a written report to Congress about the eavesdropping program. Some reports have suggested that the first briefings to Congress took place in late 2001, before the law took effect.

Among other Democrats said by Congressional officials to have received at least one briefing were Tom Daschle of South Dakota, the former Senate Democratic leader; Richard A. Gephardt of Missouri, the former House Democratic leader; and Representative Jane Harman of California, the senior Democrat on the House Intelligence Committee.

Among Republicans, the group included Senator Bill Frist, the Republican leader; Senator Trent Lott of Mississippi, the former Republican leader; Senator Richard C. Shelby of Alabama, the former chairman of the Senate Intelligence Committee; and Porter J. Goss, the current director of the Central Intelligence Agency and a former chairman of the House Intelligence Committee.

But in interviews, Mr. Hoekstra, Mr. Graham and aides to Mr. Rockefeller and Mr. Reid all said they understood that while the briefings provided by Mr. Cheney might have been accompanied by charts, they did not constitute written reports. The 2001 addition to the law requires that such reports always be in written form, and include a concise statement of facts and explanation of an activity's significance.

On Monday, Mr. Rockefeller released a copy of a classified, handwritten letter he sent to Mr. Cheney on July 17, 2003, raising objections to the program. Mr. Rockefeller has said that the rules of secrecy imposed on the briefing process left him unable to voice his concerns in public. An aide said on Tuesday that Mr. Rockefeller was "never provided with any written documentation that would qualify as formal notification" under the 1947 National Security Act.

The law requires that the executive branch notify members of Congress about continuing intelligence activities, not that it seek their consent. President Bush and other senior administration officials have argued that the briefings they provided fulfilled that legal requirement. But in interviews, some current and former members of Congress said they believe that the strict restrictions allowed lawmakers little latitude to block activities they opposed.

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