Wagner is also accused of conspiring to illegally obtain and transmit personal information on HP directors, journalists and employees as part of the computer and printer maker's crusade to ferret out the source of boardroom leaks to the media.

A call to Wagner's defense lawyer, Stephen Naratil, was not immediately returned Wednesday. An HP spokesman declined to comment.

Wagner is one of five people who were criminally charged in California state court for their alleged roles in the ill-fated spying probe at Palo Alto-based HP, the world's largest technology company.

Former HP Chairwoman Patricia Dunn, former HP ethics chief Kevin Hunsaker, and three outside investigators -- Ronald DeLia, Matthew DePante and Wagner -- all have pleaded not guilty in Santa Clara County Superior Court to four charges each of identity theft, fraud and conspiracy.

The alleged criminal behavior centers around a form of subterfuge known as "pretexting," or pretending to be someone else to trick telephone companies into coughing up personal information on customers.

The federal charges accuse Wagner of obtaining a reporter's Social Security number from other unidentified coconspirators, using that information to set up an online account with the telephone company in the reporter's name and accessing the detailed phone logs.

Wagner, of Littleton, Colo., faces up to five years in prison if he's convicted on the conspiracy charge, and a mandatory minimum of two years in prison if convicted of identity theft.

Wagner was not in custody Wednesday and an initial court appearance had not yet been set, according to Luke Macaulay, a spokesman for the U.S. attorney's office for the Northern District of California.

Macaulay said the investigation was ongoing but declined to comment on whether any others implicated in the spying scandal would be charged.

Several federal agencies and a congressional panel are investigating the behavior of HP and the third-party investigators. The charges against Wagner represent the first federal actions taken against anyone implicated in the case.

The way Wagner was charged -- he agreed to waive grand jury proceedings -- suggests he's likely cooperating with investigators aiming for more high-profile targets, said Matthew Jacobs, a former federal prosecutor in San Francisco who is now in private practice.

"The government likes to start at the lowest point in the chain of responsibility and flip people," Jacobs said. "What it signals is that the government is trying to build the case against those more senior."

Federal and state prosecutors allege that Wagner was at the bottom of a long chain of subcontractors hired to perform HP's investigation.

Dunn has acknowledged initiating the investigation but says she was unaware of the investigators' tactics. Hunsaker, who directed the investigation, left the company in September.

According to prosecutors, HP contracted the leak probe work out to DeLia, who runs a Boston-area detective firm called Security Outsourcing Solutions. DeLia in turn hired DePante's company to gather information, and DePante hired Wagner to obtain the private phone records of HP directors and journalists.

HP has remained largely unharmed on Wall Street by the scandal, as investors have cheered the company's strong operations under Chief Executive Mark Hurd and sent HP's stock price up nearly 18 percent since the investigation was disclosed in September.

However, the California attorney general's office sued HP in December, claiming the company engaged in unfair business practices, and HP agreed to pay $14.5 million to settle the claim.

A congressional panel also has demanded that Hurd explain $1.37 million worth of options he exercised just before the scandal became public. HP has said that Hurd's transactions were vetted by company lawyers and were proper.