WASHINGTON (CNN) -- A commission that investigated last year's terror attack on the U.S. diplomatic compound in Benghazi, Libya, that killed four people lacked sufficient independence and did not hold senior officials accountable, a congressional report said on Monday.
The House Oversight Committee conclusion also raised new questions about the relatively short time frame taken by the Accountability Review Board to investigate the attack by armed militants and issue its findings.
"The ARB operated under significant time pressure, completing its work and issuing a final report in just over two months," the report found.
"For some, including (the State Department), this report represented the final word on the internal failures that contributed to the tragedy in Benghazi. For others, however, the report overvalued certain facts, overlooked others, and failed to address systemic issues that have long plagued the State Department," it said.
The review board was launched by then-Secretary of State Hillary Clinton and criticized the department for failing to provide adequate security. It singled out mid-level officials.
The State Department responded on Sunday, accusing the report of "twisting the facts to advance a political agenda."
Republicans have stridently criticized the Obama administration's handling of the attack as well as security preparations in eastern Libya. Some have alleged a cover-up.
Democrats on the panel have said the committee's Republican leadership has over-politicized the Benghazi matter after a thorough investigation.
The administration has said it has cooperated fully with lawmakers, turning over documents and other information, launching the review board assessment, and sending senior officials to Capitol Hill to answer questions at public hearings.