The public could be barred from accessing some Defense Intelligence Agency records under legislation opposed by groups that advocate for civil liberties and keeping government as open as possible.

A provision included in Senate defense and intelligence bills would give the DIA's director, Army Maj. Gen. Michael D. Maples, the authority to exempt operational files from the Freedom of Information Act.

Corresponding House bills do not include the provision, and it is unclear whether that will wind up in final legislation.

Groups opposing the provision say the public access to the records is important because, for example, it recently brought to light unclassified DIA files that included photographs of prisoner abuses in Iraq and alleged criminal misconduct by agency employees.

Rep. Henry Waxman of California, the senior Democrat on the House Government Reform Committee, said Monday in a letter to House-Senate negotiators on the defense bill that the provision would further reduce public access to information.

"Open and accountable government is a bedrock principle in our democracy," Waxman wrote. "The Freedom of Information Act is one of our country's landmark laws protecting public access to government records. New exemptions should not be created lightly, especially in the absence of a hearing record that demonstrates the need for an exemption."

A DIA spokesman offered no comment Monday night.

The Sunshine in Government Initiative, a coalition of media groups that includes The Associated Press, has joined other open-government and civil liberties organizations in asking senators to eliminate the provision from the final defense and intelligence bills. The groups say that under the provision, the agency could choose to exempt unclassified materials from release.

Currently, many Central Intelligence Agency records are exempted from the FOIA because of the secrecy of the agency's methods. But media groups and civil liberties organizations argue that the DIA collects much of its information from public sources and routinely releases unclassified documents.

They say the provision is unnecessary because classified DIA documents relating to national security already are exempted from FOIA. "Declassified material has proven extremely valuable to informed debate on government policy," the Sunshine in Government Initiative said in a statement urging lawmakers to scrap the provision.