Setting the stage for a constitutional battle over the limits of state executive privilege, the Spitzer administration is refusing to cooperate with a Senate inquiry into the scandal surrounding the governor’s office’s use of state police to dig up damaging information about the Republican majority leader of the Senate, Joseph Bruno.

After having apologized repeatedly for what he described as lapses of judgment on the part of two senior administration aides who were found to have played a central role in the plot against Mr. Bruno, Mr. Spitzer yesterday abruptly shifted to an offensive posture, warning that he would repel attempts by the Senate to use its subpoena power to widen the probe of the governor’s office.

“Any new Senate hearings on this same issue would be a complete waste of state taxpayer dollars for purely partisan and political purposes,” a spokeswoman for the governor, Christine Anderson, said in a statement. “Moreover, the state Senate lacks the constitutional authority to conduct investigatory hearings into the internal operations of the governor’s office.”

A report released Monday by Attorney General Cuomo’s office found that at least two senior aides to the governor, including Mr. Spitzer’s director of communications, Darren Dopp, pressured state police to track Mr. Bruno’s use of air and ground security escorts to travel to fundraisers. The tracking was part of a plan to plant a negative story about the Senate leader in the press. The report also found that Mr. Bruno’s trips were proper.

Republicans say they are highly skeptical of Mr. Spitzer’s claim that he wasn’t aware of the plot, and they say that Mr. Cuomo’s 53-page report left crucial questions unanswered. As a result, they say they are considering launching hearings and calling senior members of the Spitzer administration, and perhaps the governor himself, to testify under oath about what involvement they may have had in the scheme.

“If there are cover-ups, the public has a right to know what has been covered up,” Mr. Bruno said, according to the Associated Press. He reportedly said the governor’s office “has seen fit to abuse the power of that office to spy and track and attempt to really destroy what apparently the governor’s office considers a political rival.”

The speaker of the Assembly, Sheldon Silver, a Democrat, urged Republicans to put the controversy to rest and said he thought the governor was telling the truth.

“I have no need to hold any hearings to go further,” Mr. Silver said in an interview. “We heard from the top law enforcement officer in the state, Andrew Cuomo. A lot of misjudgments were made, but there was no criminality.”

He said investigative hearings would “get us bogged down for a year and a half in a he-said-she-said witch hunt that will accomplish nothing but waste time.”

Mr. Silver recalled an episode in February when Mr. Spitzer sharply attacked him over their disagreement about selecting a new state comptroller. “The governor went after me at the time. That’s the nature of what we do. We are always subject to political actions,” Mr. Silver said.

The speaker said he trusted Mr. Spitzer’s claim that he was not involved in the plot and said the governor has “probably learned from the experience. We are better off as a result.”

For both Republicans and Mr. Spitzer, the choices ahead are tricky. Republicans are eager to weaken further an aggressive governor who has vowed to wrest the Senate from their majority control, but they risk facing a public backlash by prolonging the controversy through hearings. Mr. Spitzer is under immense pressure to contain the scandal but would make himself vulnerable to charges of covering up evidence if he impedes an inquiry.

Legal experts said they are unsure of the power of legislators to probe internal administration documents or to call upon officials to testify on a matter that does not currently involve any accusations of criminal wrongdoing.

In 2004, a state Supreme Court judge ruled that the Pataki administration could not withhold hundreds of pages of e-mails and memos between the governor’s office and the State Thruway Authority concerning a dispute over an Erie Canal development contract. An Assembly committee had issued a subpoena for the documents. The judge in the case reportedly concluded that the Pataki administration had failed to show that releasing the documents would be damaging to the public interest.

Asked upon what legal basis the administration has for invoking executive privilege in the event of a Senate hearing, Ms. Anderson said in an e-mail: “There were two investigations that found no violations of law. Any hearings now would be reviewing the internal deliberations of the governor’s office about legal activities, and that raises significant separation of powers issues.”

A spokesman for Mr. Bruno, John McArdle, said, “We are very confident that we have the appropriate subpoena power if we choose to use it to get to the bottom of this. If you have to hide behind executive privilege, what does that tell you?”

Mr. Cuomo’s office, in a report prepared with the Spitzer-appointed state inspector general, found that state police recreated records and took extraordinary measures to monitor Mr. Bruno’s whereabouts under the direction of a liaison to state police in the governor’s office, William Howard, and Mr. Spitzer’s communications director, Mr. Dopp, who directed the campaign under the false pretense of complying with a Freedom of Information Law request.

The governor, who wasn’t interviewed by investigators, has denied that he and his most senior aide, Secretary Richard Baum, were aware of the plot against Mr. Bruno or of the special involvement of the police, although an excerpt of a May e-mail to Mr. Baum from Mr. Dopp disclosed in the report suggests that Mr. Baum was informed, at least obliquely, about a “travel story” concerning Mr. Bruno.

Mr. Spitzer, who suspended Mr. Dopp and demoted Mr. Howard, has insisted that he and Mr. Baum were misled by Mr. Dopp and that they did not know that the administration had directed the acting police superintendent, Preston Felton, to keep track of Mr. Bruno’s whereabouts.

Messrs. Dopp and Baum both refused to speak to investigators but provided sworn statements. Mr. Baum, who has worked closely with Mr. Spitzer for almost a decade, said in his statement said he did not direct anybody to create, re-create, or maintain records relating to Mr. Bruno, but he did not say if he was aware that such orders to the police had been handed down.

While debating whether to hold hearings, Republicans yesterday were already hunting for more internal documents.

The chairman of the Senate committee on investigations and government operations, George Winner, yesterday sent a letter to Mr. Cuomo, asking him for “copies of the statements and depositions you have taken as part of your investigation, as well as copies of any e-mail messages which were reviewed during your investigatory process.”

A spokesman for Mr. Cuomo, Jeffrey Lerner, said via e-mail: “We are happy to cooperate with Senator Winner’s request to the extent the law permits.”