Washington — Forcing companies to use a government system to verify the legal status of workers would cause thousands of citizens and legal residents to be initially rejected for work and cripple the Social Security Administration, critics told Congress on Tuesday.

The system, known as E-Verify, is currently voluntary, but several proposals in Congress — including an immigration enforcement measure known as the SAVE Act — would make it mandatory.

John Trasvina, president of the Mexican American Legal Defense and Educational Fund, said that the E-Verify system relies on faulty Social Security Administration and Department of Homeland Security databases and would therefore create an official "no-work" list requiring millions of U.S. citizens and legal workers to bear the burden of proving their legal status.

"Forcing a deeply flawed system upon an unstable economy is not the answer," he told a Ways and Means subcommittee.

Using the Internet-based system, an employer can check immediately whether employees are in the United States legally by comparing their information with electronic government records.

If the information doesn't match, the employee has an opportunity to correct the paperwork, often through a trip to a Social Security office.

The panel's chairman, Rep. Michael McNulty (D-N.Y.), said he was concerned that SSA offices could be overwhelmed with a "massive new workload" as U.S. citizens and other authorized workers try to correct their information. This could hurt efforts by the agency to reduce an unprecedented backlog of disability claims, he said.

Greg Heineman, president of the National Council of Social Security Management Associations Inc., which represents 3,400 SSA managers and supervisors, predicted that making E-Verify mandatory for all U.S. employees would result in an "onslaught" of more than 10 million more visits to SSA field offices.

Rep. Heath Shuler, a North Carolina Democrat who authored the SAVE Act, said that targeting employers is the key to solving the problem of illegal immigration and that the system works.

E-Verify is free, easy to use, and allows participants to successfully match 93 percent of new hires to government databases in less than 5 seconds, Shuler said.

Of the remaining 7 percent, the vast majority do not contest the result, he added.

Shuler said every employee of a federal agency has passed through the E-Verify system.

"I have the utmost confidence in this program," he said.

The SAVE Act — or Secure America with Verification and Enforcement Act — would mandate that all businesses use the system within four years.

Several states — including Georgia, Colorado, Idaho, Minnesota, Mississippi, North Carolina, Oklahoma and Utah — have mandated E-Verify in varying degrees.