WASHINGTON - To reduce fraud and discrimination, a federal system to verify that workers are U.S. citizens or legal immigrants must use biometrics such as fingerprints or iris scans, experts told a Senate panel Tuesday.

The current E-Verify system, which checks employee-eligibility forms against records in the Social Security and Homeland Security databases, can be easily thwarted by illegal immigrants who steal or are given someone else's identity, experts said.

The only way to stop that kind of fraud is to focus on a person's unique physical characteristics to identify them, said James Ziglar, former commissioner of the U.S. Immigration and Naturalization Service and a senior fellow at the Migration Policy Institute.

The two most reliable ways to identify people are by scans of their fingerprints or irises or, ideally, both, Ziglar told the immigration subcommittee of the Senate Judiciary Committee.

"In my opinion, it would border on irresponsible not to seriously analyze the possibility of incorporating a biometric identification and verification module into the E-Verify system," Ziglar said.

In most parts of the country, use of E-Verify is voluntary. In Arizona, employers must check the eligibility of potential workers as part of the state's employer-sanctions law.

Sen. Chuck Schumer, D-N.Y., who chairs the immigration subcommittee, has begun pushing for what he called "a non-forgeable identification system" that relies on biometrics.

"This is the only way to stop future waves of illegal immigration," said Schumer, who is writing a comprehensive immigration-reform bill that he hopes to introduce this year. He has said his plan would increase border security and create a path to legalization for the estimated 12 million illegal immigrants living in the country.

The panel's senior Republican, Sen. John Cornyn of Texas, said a reliable nationwide verification system should be the foundation of any bill aimed at comprehensive immigration reform.

"We've got to get this right in order to have a crack at any reform program," he said.

A report released this week by the Migration Policy Institute acknowledged some disadvantages to a biometric system, while still saying it is the surest way to prevent identity fraud.

Among the disadvantages: cost. Employers would have to buy scanning hardware or hire companies to perform the services for them.

"Such issues could result in increased incentives for small employers not to use the system," says the report, which was written by the institute's Doris Meissner and Marc Rosenblum.

The greatest concerns would be political and philosophical, the report says.

"Many Americans . . . will object to providing the government with their fingerprints or other biometrics beyond a photo," the report says.