HACKENSACK, N.J. -- In her former job in airport security, Lisa McKenzie had a ringside seat to the world of bogus identification. She was always encountering fake Social Security cards, driver's licenses, green cards and work-authorization papers.

"I was used to seeing people who would give phony documents all the time," she said, adding that employers can do little unless they are "trained to tell real documents from the ones that aren't real."

So as human resources manager for NVC Logistics Group Inc., a logistics and transportation company in Rockleigh, N.J., McKenzie was only too happy to participate in a federal pilot program that runs online employment authorization checks against Social Security and Homeland Security databases.

Immigration officials say that more than 400 companies in New Jersey, and 10,000 nationwide, are taking part. U.S. Citizenship and Immigration Services notes that participation has more than doubled since the fall, and that nearly 200 new employers sign up every month. All told, businesses have verified the identities of more than 1 million new hires since the program began in a few states in 1997.

More than 80 percent of those whose data is run through the system are determined to be here legally, officials say.

Last week, President Bush vowed to crack down on employers who violate hiring and immigration laws. He called for the creation of a tamper-proof identification card for legal foreign workers. And he asked Congress to make the verification program mandatory and to give the Homeland Security Department enforcement powers.

In touting the program, USCIS Director Emilio Gonzalez said in a written statement: "We're protecting jobs for authorized U.S. workers."

Most employers still rely on an inspection of work and immigration documents, although few can spot phony documents, because they have grown increasingly authentic-looking.

"I'm not an immigration officer," said Judith Ayari of ComTec Inc. in Fairfield, N.J. "There are so many different classifications of immigration. There are people who are here legally on political asylum, other people on visas and other people in other categories. Then, people might be legal at one point, and their visa or other document expires. What do I do?

"I should not have to know everything about all that and have to spend hours on the telephone trying to figure these categories out and whether the person is eligible to work," she said.

The pilot program is not without its critics and there have been glitches.

For instance, the verification system has wrongly flagged some workers who are here legally, but Homeland Security officials say such instances are rare and have been quickly corrected. Employers who are part of the pilot program say such kinks pale compared with the benefits.

Those who favor strict immigration enforcement say verification will do little to significantly reduce the hiring of illegal immigrants unless participation becomes mandatory.

Groups that push for tough immigration control have long charged that U.S. government policymakers cut corners on enforcement out of fear of alienating businesses that depend on illegal immigrant labor.

"It's foolish to have it be voluntary because people who want to skirt the law don't have to do this program," said Ron Bass, the founder of United Patriots of America, based in Linden.

"There's no reason we can't track down illegal immigrants in the work force," Bass said. "Companies like FedEx and UPS track hundreds of packages a day. They tell you where those packages are at any time at any given day. Our government can do the same thing with illegal immigrants if it really wanted to."

But immigration advocates say any reform plan must take into account that undocumented immigrants are filling a crucial void in the U.S. economy.

"I don't think that an employer verification program will by itself bring any real, radical reform," said Chris Whalen, the executive director of the United Labor Agency of Bergen County. "The program only deals with the symptoms of illegal workers. But the program, and Bush's immigration policies, doesn't address why we have so many illegal workers in the United States, and why so many employers turn to them.

"Unless they face these issues, employers will continue to hire people off the books; people will continue to work off the books, and they'll continue to look for ways to get around these verification programs," Whalen said.

At a House Education and Workforce Committee hearing in July, a Southern California tomato grower, Luawanna Hallstrom, said her company lost 75 percent of its labor force soon after it was compelled to implement electronic verification of its workers. She said that despite extensive advertising, the company was unable to find Americans to work the harvest.

Hallstrom added the company lost $2.5 million because the crop could not be harvested "in a timely manner."

"Without the legal channels provided by workable guest worker programs," she said, "an enforcement-only policy directed at the border will never succeed."