Jan. 6 (Bloomberg) -- President George W. Bush's assertion that he didn't need congressional approval to authorize wiretapping without warrants isn't ``well grounded'' in law, according to a non-partisan congressional report.

The Foreign Intelligence Surveillance Act, the 1978 law that created a special court to evaluate administration wiretapping requests, doesn't exempt a National Security Agency program Bush authorized, according to a Congressional Research Service report.

``It appears unlikely that a court would hold that Congress has expressly or impliedly authorized the NSA electronic- surveillance operations here under discussion,'' the 44-page report said.

Lawmakers, including the Republican Senate Judiciary Committee Chairman Arlen Specter and Intelligence Committee Chairman Pat Roberts, as well as Democrats such as Senate Minority Leader Harry Reid are calling for hearings on the program soon after Congress reconvenes later this month.

The wiretapping program, begun after the Sept. 11 attacks, allowed the NSA to listen in without court approval on calls that involved terrorist suspects between the United States and other countries.

The nomination of Samuel Alito, Bush's pick to fill a Supreme Court vacancy, has become entangled in the controversy as senators of both parties said the nominee should disclose his position on the wiretapping.

On Dec. 19 shortly after the secret program was revealed in a New York Times article, Bush said he decided to forego the court process to track terrorist suspects and accomplices.

`Act Fast'

``To save American lives we must be able to act fast,'' Bush said in a news conference. The surveillance ``has been effective in disrupting the enemy.''

A White House spokeswoman referred questions to the NSA. A spokesman for the agency, Don Weber, declined to comment beyond previous statements made by Bush and other administration officials.

Democratic Senator Dianne Feinstein, a Judiciary Committee member and critic of the NSA program, said the report ``makes absolutely clear that the legal authorities advanced by the president in justifying domestic surveillance are on very shaky ground.''

Legal scholars said the report's conclusions aren't surprising. ``It's very clear Congress meant to prohibit what the president says he can do,'' said Philip Heymann, a law professor at Harvard University in Cambridge, Massachusetts.

Heymann said he has signed a letter drafted by David Cole, a professor at Georgetown University's law school in Washington, which condemns the president's actions.

Bush ``clearly violated the criminal prohibition'' on wiretapping, Cole said. ``He may be guilty of overreaching during a national security crisis.''

`Impossible to Determine'

The congressional report said it is ``impossible to determine'' whether the NSA overstepped constitutional boundaries without more details about the classified program. Some court cases may provide a basis for what Bush did, according to the report.

The report said the Bush administration's Office of Legislative Affairs assumes the president had the power to order wiretaps without congressional oversight.

``The administration's legal justification, as presented in the summary analysis from the Office of Legislative Affairs, does not seem to be as well-grounded as the tenor that letter suggests,'' the report said.

To contact the reporter on this story: Jeff Bliss in Washington at jbliss@bloomberg.net

Last Updated: January 6, 2006 18:05 EST