A former top lawyer for the Bush administration on Tuesday said that parts of the President Bush's controversial eavesdropping program were illegal.

There were certain aspects of the Terrorist Surveillance Program "that I could not find the legal support for," Jack Goldsmith, the former head of the Justice Department's Office of Legal Counsel, told the Senate Judiciary Committee.

But he would not say exactly what law or constitutional principle the surveillance violated. Goldsmith said the White House has forbidden him from saying anything about the legal analysis underpinning the program — key details long sought by majority Democrats and some Republicans.

Goldsmith served as the Justice Department's top legal adviser to the White House from 2003 to 2004.

The legal rationale for the program is so secretive it was initially not even shared with the general counsel of the National Security Agency, which conducted the surveillance.

Goldsmith said he assumes that the White House does not want the TSP program scrutinized.

"There's no doubt the extreme secrecy not getting feedback from experts, not showing it to experts led to a lot of mistakes," he said.

The legal justification for the president's eavesdropping program has been a central point of a standoff between the White House and Senate Judiciary Committee Chairman Patrick Leahy. The Vermont Democrat has said he wants certain information about the administration's surveillance and interrogation methods before he will schedule confirmation hearings for Michael Mukasey, Bush's choice for attorney general.

Key to the debate is a March 2004 showdown at the hospital bedside of then-Attorney General John Ashcroft as he recovered from gall bladder surgery.

Goldsmith, who was in the room, confirmed earlier accounts that Ashcroft rebuffed White House officials who were trying to get him to reauthorize the eavesdropping program. According to Goldsmith, Ashcroft said he believed the program was illegal.