The state's top elections official called for a criminal investigation of Diebold Inc. (search) as he banned use of the company's newest model touchscreen voting machine, citing concerns about its security and reliability.

The ban will force up to 2 million voters in four counties, including San Diego, to use paper ballots in November, marking their choices in ovals read by optical scanners.

Secretary of State Kevin Shelley (search) asked the attorney general's office to investigate allegations of fraud, saying Diebold had lied to state officials. A spokesman for Attorney General Bill Lockyer (search) said prosecutors would review Shelley's claims.

Diebold issued a statement saying it was confident in its systems and planned to work with election officials in California and throughout the nation to run a smooth election this fall.

The ban immediately affects more than 14,000 AccuVote-TSx (search) machines made by Diebold, the leading touchscreen provider. Many were used for the first time in the March primaries and suffered failures.

In 10 other counties, Shelley decertified touchscreen machines but set 23 conditions under which they still could be used. That order involved 4,000 older machines from Diebold and 24,000 from its three rivals.

The decision follows the recommendations of a state advisory panel, which conducted hearings earlier this month.

Made just six months before a presidential election, the decision reflects growing concern about paperless electronic voting.

A number of failures involving touchscreen machines in Georgia, Maryland and California have spurred serious questioning of the technology. As currently configured, the machines lack paper records, making recounts impossible.

"I anticipate his decision will have an immediate and widespread impact," said Kim Alexander, president of the California Voter Foundation (search) and a frequent critic of the machines. "California is turning away from e-voting equipment, and other states are sure to follow."

Activists have been demanding paper printouts — required in California by 2006 — to guard against fraud, hacking and malfunction.

Diebold has been a frequent target of such groups, though most California county election officials say that problems have been overstated and that voters like the touchscreen systems first installed four years ago.

At least 50 million voters nationally were expected to use the ATM-like machines from Diebold and other companies in November.

California counties with 6.5 million registered voters have been at the forefront of touchscreen voting, installing more than 40 percent of the more than 100,000 machines believed to be in use nationally.

A state investigation released this month said Diebold jeopardized the outcome of the March election in California with computer glitches, last-minute changes to its systems and installations of uncertified software in its machines in 17 counties.

It specifically cited San Diego County, where 573 of 1,611 polling places failed to open on time because low battery power caused machines to malfunction.

Registrars in counties that made the switch to paperless voting said Shelley's decision to return to paper ballots would result in chaos.

"There just isn't time to bring this system up before November," Kern County Registrar Ann Barnett said. "It's absurd."

Diebold officials, in a 28-page report rebutting many of the accusations about its performance, said the company had been singled out unfairly for problems with electronic voting and maintained its machines are safe, secure and demonstrated 100 percent accuracy in the March election.

The company acknowledged it had "alienated" the secretary of state's office and promised to redouble efforts to improve relations with counties and the state.