The Social Security Administration (SSA) has issued 541,000 Social Security numbers (SSNs) to illegal aliens as a result of President Barack Obama’s executive action on immigration in 2012.

The Deferred Action for Childhood Arrivals (DACA) program—which the president created in the summer of 2012 and which instructs the Department of Homeland Security (DHS) to give work permits to so-called "DREAMers"—has enabled more than half a million illegal immigrants to work legally in the United States, according to a letter from the SSA to Sen. Jeff Sessions (R., Ala.).

"By the end of FY 2014, we had issued approximately 541,000 original SSNs to individuals authorized to work under the 2012 Deferred Action for Childhood Arrivals (DACA) policy since its inception," the letter from Acting Commissioner of the SSA Carolyn Colvin said. "We do not maintain data on the number of individuals in this program who applied but were not issued SSNs under this policy."

Colvin added that the process for granting SSNs is "rigorous." Her agency currently has 6.5 million SSNs for 112-year-olds on file.

"We have longstanding, rigorous procedures for processing SSN requests," the letter said. "Under our stringent requirements, SSN applicants must present evidence of identity, age, and work-authorization immigration status."

"We will not issue an SSN if an individual has insufficient or unacceptable documentation," Colvin added.

The Washington Free Beacon previously reported that only 2.1 percent of DREAMers were denied work permits under the program.

Colvin could not give Sen. Session’s answers on how many illegal aliens have received SSNs and are receiving disability benefits under the president’s further executive action on immigration he issued last fall, since the policy was blocked by a federal judge in February.

Obama’s executive action in November would allow an additional 5 million illegal aliens to live in the United States without facing deportation.

The Deferred Action for Childhood Arrivals (DACA) program applies to illegal immigrants brought to the country before they were 16 and who are younger than 30. President Obama authorized the agency to issue work permits after legislation granting amnesty to young illegal aliens failed in the Democrat-controlled Congress in 2010.

To be eligible, applicants must have lived in the U.S. for five years, be in school or the military, and have no felonies, significant misdemeanors, or "pose a threat to national security."