CNN

WASHINGTON (CNN) – The Department of Homeland Security told its immigration enforcement agents Thursday to target employers who hire illegal workers, but also to continue to arrest the illegal immigrants it encounters.

Some Republicans said they see little change in the move.

The call by Homeland Security Secretary Janet Napolitano to focus enforcement efforts on employers comes after more than a decade of raids against companies that employ large numbers of illegal workers.

"These guidelines reflect a new department-wide focus to target, through criminal prosecution, abusive employers who cultivate illegal workplaces by breaking our country's laws and knowingly hiring illegal workers," said department spokesman Matt Chandler. "At the same time, ICE (Immigration and Customs Enforcement) will continue to arrest and process for removal any illegal workers who are found in the course of these worksite enforcement actions," Chandler said.

A copy of the confidential guidance obtained by CNN says the enforcement agency "must prioritize the criminal prosecution of the actual employers who knowingly hire illegal workers because such employers are not sufficiently punished or deterred by the arrest of their illegal workforce."

But whether the guidelines represent a departure from the policies pursued by the Bush administration was questioned by some Republicans.

"The policy does not appear to differ much from past successful ICE practices, but I plan to watch closely to see how this policy is carried out in practice," said Rep. Lamar Smith, R-Texas.

"If the administration is true to its promise about cracking down on employers who wrongly hire illegal workers, they will need to enforce all immigration laws and not a selective few," Smith said.

A former immigration official said it will be important to see whether illegal workers will be detained as prospective witnesses against employers, or whether they will be simply processed and released.

Homeland Security statistics show that last year about 6,000 workers and 135 employers were arrested as the result of worksite enforcement efforts.