The U.S. tightened its policy regarding immigrants who come to work here. President Bush signed an order that requires companies which do business with the government to ensure that their employees can legally work in the U.S.

According to The Associated Press, the White House announced Monday that firms would have to use an internet based system called E-Verify to check the Social Security numbers of their employees.

The measure comes after the Congress’ failure from last year to pass some new immigration laws. Michael Chertoff, Homeland Security Secretary said in a news conference that this order would save the federal government from awkward moments like the one where the government discovered illegal workers in some of the companies hired by them.

The private companies are not obliged to use this measure.

The measure applies to newcomers but it could affect, in a long run, millions of federal contract workers and also foreign students or persons who are waiting for their work permit.

“It is the policy of the executive branch to enforce fully the immigration laws of the United States, including the detection and removal of illegal aliens and the imposition of legal sanctions against employers that hire illegal aliens,” said the order, according to The Associated Press.

Chertoff said that about 1,000 companies a week were signing up to use the E-Verify system. The system searches through some government databases to find out if the Social Security number is correct.

The companies which don’t approve of this new law said that every system has flaws and these flaws can affect those who are legally working in the U.S. Tim Sparapani, from the American Civil Liberties Union, said that the order would cause the identity thefts to increase.

To reassure them, Chertoff said the E-Verify system is 99.5% accurate and those who face problems can solve them in less than two days.