Washington is full of people who lead double lives. They clear tables at restaurants, park cars, clean houses and run businesses.

But they are afraid of sending their children to school, buying a car, seeking medical care and even of receiving quizzical looks from strangers.

They are illegal aliens. They are afraid because there is a nationwide movement to get rid of them, largely because they are accused of taking jobs from American workers.

On Sunday, Virginia will put into force a new law intended to make it more difficult for illegal aliens to get work in the state. Its supporters hope the measure will eventually drive the illegal foreign workers out of the state's job market.

Under the law an employer - a state or local government or a private employer - can be fined as much as $1,000 and jailed for as long as a year for knowingly hiring an illegal alien. Applicants must be asked if they are in the country legally and show documents to prove it.

Virginia is estimated to have 60,000 illegal aliens in residence, of whom 30,000 live in Northern Virginia and the rest in the Tidewater area around Norfolk. Estimates of the total number in the nation range from 4 million to 12 million, Maryland believes some 65,000 illegal aliens have migrated there and a District official estimated between 50,000 and 75,000 illegal aliens live in the city.

A measure similar to the new Virginia law has been proposed on a national level by President Carter, and eight other states already have passed bills aimed at making it difficult for employers to hire illegal workers.

A bill for that purpose was recently introduced before the D.C. City Council as well.Maryland legislators last year passed a resolution urging the federal government to pass national legislation to prohibit employers from hiring illegal aliens.

The laws similar to Virginia's in force in eight states have had little effect, according to critics. They are "on the books and hardly being enforced at all. There are very few instances of any prosecutions," said immigration department spokesman Verne Jervis. The laws were passed some four years ago, Jervis said.

Local law enforcement agencies usually don't know who should enforce the law and complain that it is too difficult to determine who is in the country legally and who isn't, Jervis said.

The law that will into effect in Virginia next week is almost totally unknown, even in industries that traditionally have depended on new immigrants and foreign workers to perform service jobs.

"I didn't know about it," said Douglas Ferguson, assistant manager of the Pentagon City Quality Inn. "Possibly there might be a dishwasher or two," who is an illegal alien, he said, but "as far as I know there are no illegals."

"We have one girl from Afghanistan," said Bob Holden, manager of the Arlington Highlander Moter Inn. "She has green card (a legal permit to stay in the country). That's the only alien. I was going to get some Korean girls or Vietnamese girls to work as maids. I heard they were very, very hard workers, but I didn't have any openings."

Illegal aliens who do not have jobs are not eligible for welfare.

D.C. School Board member and minority rights activist Frank Shaffer-Corona said the new laws are a way to harass minorities and cause divisions among them. The law may also cause the firing of foreign-looking Americans because employers will be fearful that they have hired an illegal alien with forged identification. Shaffer-Corona said.

"First it makes policemen out of employers," Shaffer-Corona said. "Second it legitimizes discrimination in hiring. An employer will claim that a foreign person has false papers."

Shaffer-Corona predicted that police will try to arrest the illegal aliens and in the process sweep up legal ones as well and have them deported. He estimated the law will affect the 100,000 Latinos in Northern Virginia, about one-third of whom he said are without proper documents.

There are no good national estimates of the number of illegal aliens - some say 4 million, 8 million, 12 million, 20 million. About 60 per cent of them reportedly come from Mexico where the yearly per capita income is slightly more than $1,100 (one-seventh that of the United States).

They creep through barbed-wire and guarded borders or enter the country on limited visas as tourists or students and never go home. Agents in Mexico promise some poor workers jobs in the U.S. for a small fee, "to service the kinds of industries that need cheap labor," said Shaffer-Corona, who is also a member of a D.C. Coalition to protect undocumented workers' rights.

The name illegal alien is shunned by the workers' supporters because they feel they are not alien, i.e. Martians, and that traveling a few miles to improve conditions for their families is not a crime, Shaffer-Corona said.

The illegal aliens work as maids, parking attendants, mechanics, busboys and taxi drivers at low or below minimum wages, jobs most many Americans would not want, supporters of undocumented workers say.

"Would you like to be a dishwasher at 75 cents an hour?" Shaffer-Corona asked rhetorically. "These people are in a very deportable position. The employer says, 'You take what I give you or I'll report you.'

But Virginai Delegate William P. Robinson (D-Norfolk), the sponsor of the new Virginia law, disagrees.

"Some data indicate they were holding jobs in the category of $15,000 to $30,000 a year," Robinson said. "From the data I analyzed there's no support for the position that illegal aliens only work at jobs no one else wants.

Robinson sponsored the bill to protect at least 30,000 jobs in the Tidewater area that would have been available for his constituents if illegal aliens had not taken them, he said.