Senate Homeland Security and Governmental Affairs Chairman Joe Lieberman and ranking member Susan Collins urged the administration to immediately transfer Abdulmutallab into military custody, where he could be tried before a military commission.
In a sharply worded letter, the senators criticized the administration's decision to charge Abdulmutallab as a criminal and to read him his Miranda rights, which advised him that he could remain silent and have a lawyer.
Lieberman and Collins said he should instead be classified as an "unprivileged enemy belligerent," a legal term under the Military Commissions Act.
"The decision to treat Abdulmutallab as a criminal rather than [an unprivileged enemy belligerent] almost certainly prevented the military and the intelligence community from obtaining information that would have been critical to learning more about how our enemy operates and to preventing future attacks against our homeland and Americans and our allies throughout the world," they wrote to Attorney General Holder and John Brennan, the president's top homeland security adviser.
The Abdulmutallab case has raised fresh questions in Congress about how the administration -- and Democrats in general -- are handling national security, an issue that President Obama will likely have to address in the State of the Union he gives Wednesday night.
Lieberman and Collins also slammed the Justice Department.
"Though the president has said repeatedly that we are at war, it does not appear to us that the president's words are reflected in the actions of some in the executive branch, including some at the Department of Justice, responsible for fighting that war," they wrote.
The White House and Justice Department pointed to a statement issued Thursday when asked for comment.
"Since September 11, 2001, every terrorism suspect apprehended in the United States by either the Bush administration or the Obama administration has been initially arrested, held or charged under federal criminal law," that statement said.
"In the hours immediately after Abdulmutallab allegedly attempted to detonate an explosive device on board a Northwest Airlines flight, FBI agents who responded to the scene interrogated him and obtained intelligence that has already proved useful in the fight against Al Qaeda," it said.
The statement added that charging Abdulmutallab under the laws of war or referring him for prosecution before a military commission would not force him to divulge intelligence or prevent him from obtaining an attorney.
Senate Intelligence Chairwoman Dianne Feinstein and ranking member Kit Bond are reviewing how the administration has handled Abdulmutallab as part of a wider probe into the bombing attempt.
On Thursday, Bond told reporters he was especially concerned that reading Abdulmutallab his Miranda rights "may have cut off valuable information."
Feinstein added she was concerned that the administration did not consult senior intelligence and homeland security officials, including Director of National Intelligence Dennis Blair, before charging Abdulmutallab as a criminal.
To that end, Collins and Lieberman introduced a bill last week that would require the administration to consult the director of national intelligence, secretaries of the Homeland Security and Defense departments, and the director of the National Counterterrorism Center before interrogating and charging suspected foreign terrorists.