Republicans in Congress have launched a major offensive to force several million undocumented immigrants to leave the United States with a bill that would make it mandatory for U.S. employers to electronically verify workers’ legal status. It sounds like a reasonable idea, but the way they want to do it would hurt all involved.

Last week, House Judiciary Committee Chairman Lamar Smith , R-Texas, and 11 fellow Republicans introduced the so c-called E-Verify bill, which would require employers to use an existing Homeland Security Department database to check the legal status of newly hired employees. According to Congressional sources, it has a good chance of passing the Republican-controlled House.

A companion bill in the Senate was sponsored by Sen. Chuck Grassley, R-Iowa, and co-sponsored by nine fellow Republicans, including Florida’s Marco Rubio. Its fate in the Democratic-controlled Senate is not clear.

Supporters of the E-Verify system argue that it is already mandatory in states such as Arizona, Georgia and Alabama, and that it works. Smith’s bill would give most employers up to two years to use E-verify for new hires and would give employers the choice of using the system for existing workers.

“With unemployment at 9 percent, jobs are scarce,” Smith says in his website. “Despite record unemployment, 7 million people work in the U.S. illegally. These jobs should go to legal workers.”

He adds: “It takes just a few minutes to use and easily confirms 99.5 percent of work-eligible employees.”

Sounds perfectly logical. But when you look into it a bit closer, you realize that, barring broader measures to solve the U.S. immigration mess, it may do more harm than good.

Critics of the bill say mandatory use of E-verify would badly hurt many industries, push undocumented immigrants further into the underground economy, and mistakenly cause many legal residents to lose their jobs because of the database’s mistakes.

Among their arguments:

•  The E-Verify system is imperfect. The near absolute accuracy rate cited by Smith is misleading, because it only refers to verification of workers with legitimate documents. E-Verify fails to identify undocumented workers in 50 percent of the cases, because many of them present valid documents belonging to other people, critics say.

Also, the database often mistakenly flags Hispanics with common names, such as Perez or Rodriguez, because of identity confusion or inconsistencies in their various U.S. documents. Naturalized U.S. citizens are 32 times more likely to be erroneously flagged by the E-Verify system than U.S.-born citizens, according to the National Immigration Forum, a pro-immigration advocacy group.

•  If E-Verify becomes law, many businesses that rely heavily on undocumented workers, such as Florida and California agricultural firms, would go out of business or move operations to other countries. The idea that millions of unemployed Americans would take the jobs of Mexican or Central American undocumented field hands is unrealistic. Few American workers are willing to work in back-breaking jobs harvesting oranges or vegetables under the sweltering sun for minimum pay.

•  If E-Verify goes through the way it is, many employers would simply tell their undocumented workers: “I can’t have you on the books, so I’ll pay you off the books.’’ That would make undocumented workers even more vulnerable to exploitation, would drive down wages for both legal and illegal workers, and would cost the government a loss of more than $17 billion in revenue over the next 10 years, according to General Accounting Office estimates.

My opinion: E-Verify is a legitimate tool that could help solve the U.S. immigration crisis, but only if it is implemented alongside a path to legalization for undocumented workers who are willing to pay fines and learn English.

Otherwise, it will only help push millions of people further into the underground economy, and may cause thousands of legal residents — mostly Hispanics — to lose their jobs because of documentation mistakes.

Whoever thinks that millions of undocumented immigrants, many of whom have American children, would simply leave their families behind and go back to their home countries is either kidding himself, or is trying to take the rest of us down the dangerous road of blaming immigrants for the U.S. economic crisis.