Paperless electronic voting machines used throughout the Washington region and much of the country "cannot be made secure," according to draft recommendations issued this week by a federal agency that advises the U.S. Election Assistance Commission.

The assessment by the National Institute of Standards and Technology, one of the government's premier research centers, is the most sweeping condemnation of such voting systems by a federal agency.

In a report hailed by critics of electronic voting, NIST said that voting systems should allow election officials to recount ballots independently from a voting machine's software. The recommendations endorse "optical-scan" systems in which voters mark paper ballots that are read by a computer and electronic systems that print a paper summary of each ballot, which voters review and elections officials save for recounts.

Voters in Maryland cast ballots on electronic machines that produce no paper record of each vote; in the District and Loudoun County, voters can choose between using such machines and optical-scan systems. Other Northern Virginia jurisdictions, and many counties across the state, use electronic voting systems exclusively.

NIST's recommendations are to be debated next week before the Technical Guidelines Development Committee, charged by Congress to develop standards for voting systems. To become effective, NIST's recommendations must then be adopted by the Election Assistance Commission, which was created by Congress to promote changes in election systems after the 2000 debacle in Florida.

If the commission agrees with NIST, the practical impact may not be felt until 2009 or 2010, the soonest that new standards would be implemented. The standards that the Election Assistance Commission will adopt are voluntary, but most states require election officials to deploy voting systems that meet national or federal criteria.

State election officials in Maryland and Virginia declined to comment yesterday on the NIST report, which they were reviewing.

Alice P. Miller, executive director of the District's Board of Elections and Ethics, said through a spokesman that she would not comment because she is a member of the Technical Guidelines Development Committee.

NIST says in its report that the lack of a paper trail for each vote "is one of the main reasons behind continued questions about voting system security and diminished public confidence in elections." The report repeats the contention of the computer security community that "a single programmer could 'rig' a major election."

Fears about rigging have animated critics for years, but there has been no conclusive evidence that such fraud has occurred. Electronic voting systems have had technical problems -- including unpredictable screen freezes -- leaving voters wondering whether their ballots were properly recorded.

Computer scientists and others have said that the security of electronic voting systems cannot be guaranteed and that election officials should adopt systems that produce a paper record of each vote in case of a recount. The NIST report embraces that critique, introducing the concept of "software independence" in voting systems.

NIST says that voting systems should not rely on a machine's software to provide a record of the votes cast. Some electronic voting system manufacturers have introduced models that include printers to produce a separate record of each vote -- and that can be verified by a voter before leaving the machine -- but such paper trails have had their own problems.

Printers have jammed or otherwise failed, causing some election directors to question whether a paper trail is an improvement. Maryland state elections administrator Linda Lamone, in an undated video snippet that her critics have circulated on the Internet, says that voter verification is unnecessary. "I'm not going to put this paper on my machines -- it'll be over my dead body, because I just don't think it works. It really is a false sense of security," she said.

For critics of paperless electronic voting, the report is vindication. "I think I got it right," said Aviel Rubin, a Johns Hopkins University computer scientist who has long questioned the security and reliability of some electronic voting systems.

Linda Schade, a founder of TrueVoteMD, which has pressed for a system that provides a verifiable paper record of each vote, said, "These strong statements from a credible institution such as NIST add yet another voice to the consensus that paper electronic voting as used in states like MD is not secure. We hope that the [Election Assistance Commission] formally adopts these improved standards."

Even critics of paperless electronic voting have grown disenchanted with the practical problems of adding printers to electronic "touch-screen" voting machines.

"Why are we doing this at all? is the question people are asking," said Warren Stewart, policy director of VoteTrustUSA, a group critical of electronic voting systems. "We have a perfectly good system -- the paper-ballot optical-scan system."