The U.S. Supreme Court let stand Tuesday an immunity law on wiretapping viewed by government as a useful anti-terror tool but criticized by rights activists as a flagrant abuse of executive power.

The top U.S. court declined to review a December 2011 appeals court decision that rejected a lawsuit against AT&T for helping the National Security Agency monitor its customers' phone calls and Internet traffic.

Plaintiffs argue that the law allows the executive branch to conduct "warrantless and suspicionless domestic surveillance" without fear of review by the courts and at the sole discretion of the attorney general.

But President Barack Obama's administration has argued to keep the immunity law in place, saying it would imperil national security to end such cooperation between the intelligence agencies and telecom companies.

"Electronic surveillance for law enforcement and intelligence purposes depends in great part on the cooperation of the private companies that operate the nation's telecommunication system," the Obama administration said while making its case.

"If litigation were allowed to proceed against those who allegedly assisted in such activities, the private sector might be unwilling to cooperate with lawful government requests in the future, and the possible reduction in intelligence that might result is simply unacceptable for the safety of our nation," it stressed.

The Supreme Court is set to hear a separate case later this month in which civil liberties' group are suing NSA officials for authorizing unconstitutional wiretapping.

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