The Obama administration is again invoking government secrecy in defending the Bush administration's wiretapping program, this time against a lawsuit by AT&T customers who claim federal agents illegally intercepted their phone calls and gained access to their records.

Disclosure of the information sought by the customers, "which concerns how the United States seeks to detect and prevent terrorist attacks, would cause exceptionally grave harm to national security," Justice Department lawyers said in papers filed Friday in San Francisco.

Kevin Bankston of the Electronic Frontier Foundation, a lawyer for the customers, said Monday the filing was disappointing in light of the Obama presidential campaign's "unceasing criticism of Bush-era secrecy and promise for more transparency."...