The white van eases into a liquor store parking lot and is swarmed by 30 Hispanic day laborers who begin intense job negotiations with the driver. Within seconds, another wave of people descend on the van. Mostly white and middle aged, they snap pictures as they cite federal labor laws.

"If you hire illegal workers, we'll put your picture on the Internet," warns Robin Hvidston, a property manager who became an immigration activist after being alarmed by the number of Hispanics she saw in her Orange County community.

"I hire the legals," the driver, who later identifies himself as Iranian, replies in broken English.

"But these people are not legal," retorts protester Gerry Nance, handing the driver tax and employment eligibility forms. "You must check all this to be sure."

The driver shakes his head and drives off. The would-be workers return to the wall of the liquor store, disappointed but hopeful the protesters will leave so they can hook a day's worth of wages.

Frustrated by the federal government's response to illegal immigration and worried that undocumented workers are depressing wages, conservative immigration reform groups are broadening their focus from the U.S.- Mexico border to the workplace -- in Southern California, Texas, Chicago, Virginia and elsewhere.

Their method: Take photos of construction bosses and anyone else picking up day laborers, then post the photos on Web sites (such as www.wehirealiens.com and www.operationshameonyou.org), sometimes including home addresses and license plate numbers. They also turn their footage into immigration officials.

Their objective is twofold -- shame businesses into not hiring undocumented workers and force the government to enforce immigration law.

"We knew we would need a two-pronged approach to force the government to deal with this issue," said Chris Simcox, a former school teacher who co-founded the Minutemen, which began civilian border patrols in Arizona a year ago and is now focusing on employers. "Now we want to video tape, expose and embarrass the businesses breaking the law."

The tactics anger business owners, who are threatening lawsuits.

"These are just personal attacks and they are all false," said Elias Zepeda, accounts manager for Strong Terminators, a termite company in Downey, Calif. that appears on wehirealiens.com. "That's why we are talking to lawyers."

A dozen other businesses with pictures on such sites declined comment, though another owner who did talk briefly denied hiring illegal workers and said he was preparing a slander lawsuit against wehirealiens.com.

While immigration authorities have made efforts to strengthen border security by hiring thousands more agents, illegal workers are rarely picked up on the job, and businesses hiring them are almost never fined.

An average of 200 workers nationwide were arrested each week during the 1990s, dropping to about 8 a week by 2003, the last year of available data.

Conservatives alarmed by illegal immigration realize that going after businesses may be even more important than strengthening the border, said Mark Krikorian, executive director of the Center for Immigration Study, which favors less immigration and stricter enforcement.

"These startup groups suggest an increasing sophistication in the immigration debate," Krikorian said.

U.S. Immigration and Customs Enforcement officials evaluate the groups' phone tips and footage, but often their reports are not verifiable enough to prompt an investigation, said Bill Riley, ICE's chief of work site enforcement.

"We'll ask them, 'How do you know they are illegal?"' said Riley. "If they say, 'They look foreign,' that obviously isn't enough."

Though too early to judge their impact, camera-toting protesters do appear to limit the number of workers picked up on any given day.

During three hours at the recent morning protest organized by a group called the Fire Coalition in Lake Forest, an Orange County city 50 miles south of Los Angeles with a large Hispanic population, only one employer ignored the protesters and picked up a day laborer.

About a dozen construction company vehicles entered the parking lot, only to pull away quickly.

"Nobody gets work on the days they come," said Fernando Gomez, a day laborer who sipped coffee to keep warm. "They (the protesters) don't let the bosses even come up to us, but you know their kids are not going to do this hard work."

Gomez, 30, from Michoacan, Mexico, said he and most day laborers he knows came to the U.S. illegally.

"But someday we will be legal," he said. "We just want to work. We didn't come to do anything bad to anybody."

Drivers of some passing cars honked and gave words of encouragement to the protesters, while others unleashed vulgarities.

"Why don't you guys get a life," yelled a Hispanic man who pulled into the liquor store parking lot. "It's Maria cleaning your toilet and Pedro doing the landscaping at your house. Accept it."

The comments set off a screaming match between the man and two protesters.

Liquor store co-owner Joga Siph said a month ago he called the police on the protesters because they were blocking the store entrance. Protesters have since agreed to keep some distance.

"The workers don't bother us," said Siph. "They come, buy something and wait outside a few hours for work."

In Houston, a group called "Operation Spotlight" began protesting and taking pictures at day labor sites last month, forcing two sites to close temporarily.

In Herndon, Va., just outside Washington, D.C., members of the Herndon Minutemen have filed a suit against the town council for voting to set up a day labor site with public money, said group founder George Taplin.

Taplin said the scheduled Dec. 19 site opening would give his group a clear target.

"All we have to do is just stand there with our cameras," said Taplin. "Nobody is going to show up."

A similar suit has been filed in Phoenix, with others planned in suburbs of Chicago and Washington, D.C., said Simcox of the Minutemen.

"It's a headache when these groups are filming and going to the cities to complain," said Victor Narro, project director of the UCLA Downtown Labor Center, a university affiliate that helps defend day laborers' rights. "But they are part of today's immigration reality."