Illinois Democrat Sen. Tammy Duckworth sent a letter to the Transportation Security Administration on Friday demanding the agency rescind its "shoes-on" policy, according to a report.

In a letter obtained by CBS News, Duckworth called the policy a "reckless act" that may be placing flight passengers at risk.

Duckworth also warned that the policy was likely implemented "without meaningful consultation with TSA," citing an investigation by the Department of Homeland Security's inspector general that found it created a new security vulnerability in airport screening systems.

The IG's classified report found that TSA scanners are unable to effectively screen shoes, raising concerns that threat items could evade detection. The report was allegedly buried by DHS leadership, CBS News previously reported.

Duckworth said that the watchdog flagged the issue as urgent to then-Homeland Security Secretary Kristi Noem, but no corrective action was taken.

She said that failure was "outrageous, unacceptable and dangerous to the flying public."

"Allowing a potentially catastrophic security deficiency to remain in place for seven months and counting betrays TSA's mission," Duckworth wrote. "At a minimum, TSA's failure to swiftly implement corrective action warrants the immediate withdrawal of Secretary Noem's reckless and dangerous policy that increases the risk of a terrorist smuggling a dangerous item onto a flight."

Duckworth wrote the letter to acting TSA Administrator Nguyen McNeill, arguing that TSA's lack of response may violate federal law. She added that TSA missed a legally required 90-day deadline to outline corrective actions after receiving the IG's findings.

"Such inaction violates Federal law, Office of Management and Budget (OMB) guidance and DHS's own directives," Duckworth wrote.

DHS lifted the rule to remove shoes and implemented a "shoes-on" policy in July. The department argued that the decision would not impact security standards due to "our cutting-edge technological advancements and multi-layered security approach."

DHS and TSA didn't immediately respond to the news outlet's requests for comment.

In December 2001, roughly three months after the 9/11 terror attacks, Richard Colvin Reid, a British terrorist who became known as the "shoe bomber," boarded an American Airlines flight from Paris and Miami wearing shoes packed with explosives that he unsuccessfully tried to detonate. This incident led to the TSA's 2006 policy requiring passengers to remove shoes at security.