A federal judge resigned from a special court to protest President George W. Bush's secret authorization of a warrantless domestic spying program, The Washington Post reported Wednesday.

Though no explanation provided in his resignation letter, U.S. District Judge James Robertson privately expressed deep concern that the surveillance program that Bush authorized was legally questionable and may have tainted the work of the court, the report said.

Robertson was one of the 11 members of the secret Foreign Intelligence Surveillance Court (FISC). For more than 25 years, the court has served as the only body that could legally authorize secret surveillance of espionage and terrorism suspects.

Citing colleagues of Robertson, the Post said the judge had indicated he was concerned that information gained from the warrantless surveillance under Bush's program could have then been used to obtain warrants under the FISC program.

Supreme Court spokeswoman Kathy Arberg said early Wednesday she had no information to offer on the matter.

Some FISC judges said they were saddened by the news of Robertson's resignation and wanted to hear more about the president's program, the report said.

Robertson, appointed to the federal bench in 1994, was later selected to serve on the FISC court. He often ruled against the Bush Administration's assertions of broad powers in the terrorism fight.

According to the previous report, soon after the Sept. 11 terror attacks in 2001, Bush secretly authorized domestic eavesdropping despite legal prohibitions against the practice.

Under this authorization, the National Security Agency (NSA) eavesdropped, without warrants, on as many as 500 people inside the United States at any given time since 2002.

Source: Xinhua