Hundreds of thousands of illegal immigrants could receive health care coverage from their employers under the bills winding their way through Congress, despite President Obama's explicit pledge that illegal immigrants would not benefit.
The House bill mandates, and the Senate bill strongly encourages, businesses to extend health care coverage to all employees. But the bills do not have exemptions to screen out illegal immigrants, who usually obtain jobs by using false identities and are indistinguishable from legal workers.
A rough estimate by the Center for Immigration Studies suggests that the practical effect of the mandates would be that about 1 million illegal immigrants could obtain health insurance coverage through their employers.
"It's possible an employee could deceive an employer with a fraudulent document, just as under current law, to gain employment, just as it's possible for all sorts of criminal activity to occur, and why we have law enforcement," said Nadeam Elshami, a spokesman for House Speaker Nancy Pelosi, California Democrat, who wrote the final House bill.
Republicans said that loopholes in the bill could allow coverage to just about any illegal immigrant who wants to cheat the system.
"This is a complete cover-all-the-gaps federal health insurance for illegals, whether it be under Medicaid, the refundable tax credit or whether it be under their employers who would not be able to verify their employers unless we fix E-Verify," said Rep. Steve King of Iowa, the top Republican on the House Judiciary Committee's immigration subcommittee.
How to deal with immigrants, both legal and illegal, remains one of the thorniest issues in the health care debate. In his address to a joint session of Congress in September, Mr. Obama specifically challenged Republicans who said his plans would extend coverage to illegal immigrants.
That statement elicited an outburst of "You lie" from Rep. Joe Wilson, South Carolina Republican.
Most of the focus has been on whether the bills in the House and Senate go far enough to screen out illegal immigrants applying for public benefits. The Senate bill is generally considered to have stronger provisions than the House version to exclude participation by illegal immigrants.
The employer mandate could play a major role in coverage for illegal immigrants, but the effect has not been widely understood.
Steven A. Camarota, research director for the Center for Immigration Studies, said about 6.5 million illegal immigrants work in the United States, though nearly half do so off the books and wouldn't be counted for purposes of employer-sponsored health insurance.
Of those who work on the books, about 2.3 million already have insurance through their employers. That leaves at least 1 million who would need insurance and could obtain it from an employer under the proposed mandates.
"It's definitely significant," Mr. Camarota said.
Democrats said their bill doesn't change eligibility for benefits for illegal immigrants but it does change laws on who must provide insurance. Any employer with a payroll higher than $500,000 would be required to provide insurance for employees.
The House bill offers tax credits for two years to help small businesses provide insurance, including businesses that hire illegal immigrants.
But Mr. Elshami said businesses are already prohibited from hiring of illegal immigrants.
The Senate bill is more complex. It would urge companies to provide insurance, then penalize them for each employee who applies for credits for the health care exchange.
Jim Manley, a spokesman for Senate Majority Leader Harry Reid, Nevada Democrat, said the bill includes a screening process to keep illegal immigrants from getting credits in the health care exchange. But even illegal immigrants would be counted in the penalty against employers, so companies would be paying for having hired them.
"In this scenario, an employer would have to provide a responsibility payment for an undocumented worker. But that undocumented worker wouldn't be getting coverage through the exchange," Mr. Manley said.
Robert Rector, a senior research fellow at the Heritage Foundation, called the debate "an absolute charade" because Mr. Obama and Democratic leaders have signaled their intent to try to pass a bill legalizing illegal immigrants next year.
Once their legal status is secured, Congress would have to decide their eligibility for public benefits. Democrats have been pushing for broad inclusion, and their health care proposals give equal treatment to legal immigrants and citizens.
Republicans say the government should do more to push for a legal work force in the first place.
"If it was not bad enough that illegal immigrants take jobs that rightfully belong to citizens and legal immigrants, now they will get health care benefits that should go to Americans," said Rep. Lamar Smith of Texas, the top Republican on the House Judiciary Committee. "If they were not in the country, we wouldn't have to worry about emergency room or health insurance costs at all. And Americans would have these jobs."
A Congressional Research Service report notes that the House Democrats' bill does not expressly prohibit illegal immigrants from getting health insurance and, in fact, would mandate that they obtain insurance if they meet the "substantial presence test."
That test calculates U.S. residency based on the number of days per year a person is in the country.