Thirty-nine million Americans potentially had information relating to their personal identities compromised by illegal immigrants over the course of four years, according to government documents obtained by the Immigration Reform Law Institute (IRLI).

Social Security Administration records gleaned through a Freedom of Information Act (FOIA) lawsuit by IRLI indicate that between 2012 and 2016 there were 39 million instances where names and Social Security numbers provided on W-2 tax forms failed to match corresponding data on file with the federal government.

In a statement announcing the discovery on Tuesday, IRLI's Executive Director and General Counsel Dale Wilcox said the lawsuit was undertaken to ascertain how deep the problem of identity theft by illegal immigrants ran, especially in light of arguments painting unlawful immigration as a "victimless crime."

"This investigation shines a light on the depth of America’s problems as a result of allowing illegal aliens into the country," Wilcox said. "It also debunks the idea that being in the country illegally is a victimless crime."

Wilcox added that many of the victims of identity theft were children and thereby unable to defend themselves appropriately.

"Millions of Americans, in many cases children, are having their identities stolen to enable even more criminal activity," he said. "Illegal aliens should not reap Social Security benefits that result from the commission of identity theft."

ILRI is the legal arm of the Federation for American Immigration Reform, a non-profit group that advocates for a stronger U.S. border control policy.

In April, the group filed a federal lawsuit against the Social Security Administration pertaining to records relevant to an Obama administration decision to cease sending "no match" letters. The letters, which the federal government had relied upon since 1979 to prevent identity theft, inform employers that the name and Social Security number given by an employee does not match official records.

The Obama administration stopped sending "no match" letters after putting into place the Deferred Action for Childhood Arrivals (DACA) program in 2012, according to The Washington Times. DACA, which granted legal protections to nearly 800,000 illegal immigrants brought to the U.S. as children, was revoked by President Donald Trump in September 2017.

Earlier this summer, the Trump administration also unveiled plans to begin sending "no match" letters again to employers starting in spring 2019 as part of its efforts to crack down on illegal immigration.

This is not the first time "no match" letters have been at the center of political controversy.

Shortly after taking office, President Barack Obama's Department of Homeland Security (DHS) rescinded a 2007 directive by the Bush administration, which was never implemented, that would have sent the letters to 140,000 employers mandating they address discrepancies involving nearly 9 million individuals. The directive arose after Congress failed to pass a comprehensive immigration reform proposal championed by the late Sen. Ted Kennedy (D., Mass.) and then-President George W. Bush. The directive would have given employers 90 days to resolve existing inconsistencies—either by confirming the identity of individuals in question or firing them—before initiating criminal penalties.

Before the directive could be implemented under Bush, the AFL-CIO and the American Civil Liberties Union filed a lawsuit in federal court, arguing "inaccuracies" in data collected by the Social Security Administration would affect U.S. citizens and legal immigrants alike. Subsequently, the matter was tied up in federal court until the end of the Bush administration. The Obama-era DHS did not resume sending out "no match" letters until 2011, before suspending the program again in 2012 when DACA was implemented.

When declaring ILRI's suit in April, Wilcox lambasted the Obama administration for allowing employers "to exploit" lax immigration laws while millions of Americans "had their personal data stolen."

"Ending the no-match letters policy was yet another disastrous move by the previous administration and allowed unscrupulous employers to exploit illegal aliens while avoiding prosecution by federal authorities," Wilcox said at the time. "It also caused great damage in the lives of those who had their personal data stolen and used to enable further violations of our immigration laws. The American people deserve to know the facts behind why this decision was made."