Recent enhancements to the system include a photo-screening tool for biometric verification and the availability of naturalization data that can confirm the citizenship status of recently naturalized U.S. citizens. As of this coming May, all federal contractors and subcontractors will have to start using the program when hiring new employees.

The version of the passed last week by the , included the E-verify mandate. But that provision has been culled from the Senate version -- prompting frantic lobbying on both sides of the issue to either put it back into the legislation or leave it out permanently.

Steven Camarota, director of research at the (), a Washington D.C.-based immigration watchdog group, estimated that failing to properly vet the employment eligibility of workers under the stimulus plan could result in a large number of undocumented workers getting taxpayer-funded jobs. That could be especially true of the construction sector, where nearly 15% of the workers are illegal immigrants, Camarota claimed.

Camarota argued that there is little reason to oppose the E-Verify program and said that concerns about its reliability have been overstated. He noted that the number of instances where the E-Verify system had mistakenly fingered a worker as being unauthorized for employment was a "tiny fraction" of the overall number of eligibility checks made by employers. In cases where mistakes are made, the process allows for remediation, Camarota said.

He was also skeptical of claims that the E-Verify system would be unable to handle a sudden large-scale increase in employment eligibility checks, noting it already processes millions of queries. "If there are still bugs to be worked out, including the stimulus jobs would be good thing," because it would prompt quicker remediation, he said.