Contractors working with Baltimore County could soon be required to verify the immigration status of their employees or risk losing county business.

The County Council enacted a resolution Monday, by a unanimous vote of the six members that were present. The resolution urges County Executive James T. Smith Jr. to ensure contractors vet new hires with the federal E-Verify program. The free, online system, operated by the Department of Homeland Security and the Social Security Administration, allows an employer to compare details from a new hire's employment eligibility form with information from more than 500 million federal records.

"Basically this has the teeth of a law," said John E. Beverungen, county attorney. "But in this case, the text says 'request.' It looks like at the minimum this will start the discussion."

Several area construction unions had urged officials to take the action, which they said would save their members' jobs.

The resolution was drafted to "make sure we are not taking jobs away from those who should have them," said Council Chairman John Olszewski, who co-sponsored the measure with Councilman Kenneth N. Oliver.

Those businesses that knowingly hire undocumented migrant workers could lose their contracts as well as the ability to bid on future work.

Representatives of Casa de Maryland, an immigrants advocacy group, and the ACLU questioned the accuracy of E-Verify and asked council members to review several reports on it.

"While I respect the desire to ensure the lawful ability to work in the U.S., I disagree with the means to do so," said Ajmel Quereshi, an attorney for the ACLU.