Although armed with subpoena power, the New York State Office of the Inspector General completed an investigation of the Spitzer administration’s plot against a political rival without interviewing two key aides to the governor, issuing any subpoenas, or preparing any final report, a spokesman for the office said.

Unlike Attorney General Cuomo’s office, which conducted a separate, concurrent investigation into the matter, the state inspector general had the subpoena power to compel the two aides — Mr. Spitzer’s communications director, Darren Dopp, and chief of staff, Richard Baum — to testify under oath and force the administration to turn over e-mail records.

A spokesman for the inspector general’s office, Stephen Del Giacco, declined to say why the office did not issue any subpoenas. In response to questions, he said repeatedly: “We concurred with what the attorney general found.”

The news that the inspector general, Kristine Hamann, a Spitzer appointee, chose not to use her office’s subpoena power has increased suspicion among Senate Republicans that the office’s probe was biased toward the governor and incomplete, and it prompted more calls for further inquiry into the scandal.

“I don’t think there was a report or an investigation,” a spokesman for the Senate Republicans, John McArdle, said. “I don’t think they did anything, period.”

State Senator George Winner, a Republican who has submitted letters to the inspector general’s office and the attorney general’s office asking to review e-mails, testimonial transcripts, and other supporting documents, said the inspector general “didn’t do anything but be a convenient foil to allow the governor to say he’s been exonerated by his own agency.”

Mr. Spitzer has described the inspector general’s investigation as “independent,” and in defending himself has pointed to the office’s finding that the administration did not commit any illegal activity.

Ms. Hamann, a former prosecutor in the Manhattan district attorney’s office, said in a July 23 statement that her office agreed with the conclusions drawn by the attorney general’s office, which faulted two Spitzer aides, Mr. Dopp and the governor’s liaison to the state police, William Howard, for their roles in the plot against the Republican Senate majority leader, Joseph Bruno, and also found no evidence of criminal wrongdoing.

A report issued by the attorney general’s office last week found that the two aides led a campaign to discredit Mr. Bruno that involved asking police to take special measures to monitor Mr. Bruno’s use of air and ground security escorts on days he attended fund-raisers and leaking the travel records to the Times Union of Albany.

Mr. Spitzer insists that proper punishment has been meted out; he indefinitely suspended Mr. Dopp and demoted Mr. Howard. Senate Republicans say they suspect knowledge of the plot went farther up the chain of command and have focused their scrutiny on Mr. Baum, who said he thought that Mr. Dopp had been responding to a proper press request and said he was unaware that the state police had taken special measures to keep track of Mr. Bruno.

A spokesman for the attorney general said investigators in the office sought to interview Messrs. Dopp and Baum. Following the advice of the administration’s top legal counsel, David Nocenti, the two aides declined to be interviewed and submitted sworn statements. All e-mails provided to the attorney general’s office and the inspector general’s office by the Spitzer administration were handed over voluntarily.

Mr. Spitzer told the New York Times on Friday that he would allow Messrs. Dopp and Baum to testify before the State Ethics Commission, which is conducting a preliminary review of the scandal and may launch a full probe. Senate Republicans are also considering whether to conduct their own inquiry.