The ACLU on Thursday excoriated President Obama for continuing the Bush administration's strictest national security policies, including indefinite detention, military commissions and a "targeted kill" program that authorizes the government to take out suspected terrorists anywhere.

The American Civil Liberties Union warned Mr. Obama, in a report based on a review of his 18 months in office, that his administration was on course to institutionalize the policies of his predecessor. The ACLU was a fierce critic of President George W. Bush's war on terror.

Failing to overturn those and other contentious tactics risks the creation of a "new normal," the ACLU argued in the report, which looked at administration policies it says implicate human rights and civil liberties.

"President Obama began his presidency with a bang, signing executive orders that placed the power of the presidency behind the restoration of the rule of law and gave meaning to the president's stated view that America must lead with its values," said Anthony D. Romero, the ACLU's executive director. "Unfortunately, since that time, the administration has displayed a decidedly mixed record resulting, on a range of issues, in the very real danger that the Obama administration will institutionalize some of the most troublesome policies of the previous administration."

The ACLU praised Mr. Obama, however, for putting an end to the use of so-called enhanced-interrogation techniques and for publishing Bush-era memos outlining their legal justifications in the name of transparency.

Indeed, Mr. Obama signed two sweeping executive orders upon taking office that sought to undo some of Mr. Bush's most controversial policies: outlawing tactics he deemed as torture and ordering the closure of the prison at U.S. Naval Base Guantanamo Bay, Cuba. Both steps were widely hailed by civil liberties groups, but implementation of the latter has proved elusive as Congress has thwarted Attorney General Eric H. Holder Jr. from following through on the effort.

As a consequence, the administration has continued to hold detainees at the prison without trial as officials figure out what to do with them, a practice that he criticized as a senator. Meanwhile, though the Justice Department has chosen to try several high-profile suspected terrorists in federal courts, it has continued to use the military commission system at Guantanamo originally set up by Mr. Bush, albeit with reforms enacted by Congress.

Asked about the ACLU's report Thursday, White House press secretary Robert Gibbs cited those reforms, aimed at making the system more fair, and noted there are critics at each end of the political spectrum.

"At almost every opportunity, somebody, I think wrongly, suggests that our policies are markedly different from, or that our policies are such that they won't keep us safe and criticize the positions that the president has taken. So it's ironic now that in the same argument there's somebody who says they're completely the same," he told reporters.

The ACLU report said Mr. Obama's decision to release Justice Department memos was good for transparency and allowed the American people to judge Mr. Bush's policies to determine whether they were conceived in good faith. But it criticized Justice attorneys for Mr. Obama for not pursuing those who authorized "torture" and for fighting the release of additional documents regarding the interrogation program.

The ACLU also hit the administration for subsequently fighting the release of photos of detainees allegedly being mistreated in Iraq and Afghanistan by supporting legislation that allowed the Pentagon to block their release.