ALBANY, N.Y. (AP) – The state Ethics Commission will investigate the scandal in which top aides to Governor Spitzer used state police in a plot to discredit Republican Senate leader Joseph Bruno, according to a letter obtained by The Associated Press.

The letter dated today says the state Ethics Commission, which has subpoena power, will investigate the case that has dominated the Albany agenda since an investigative report was released Monday by state Attorney General Andrew Cuomo.

The letter addressed to Mr. Cuomo was provided by a state official on the condition of anonymity because the investigation hadn’t been officially announced. When told of the letter, state Ethics Commission spokesman Walter Ayres confirmed it came from the investigative agency.

The commission seeks all interview transcripts, notes, e-mail and other material from Mr. Cuomo’s investigation, but it can compel testimony under oath. Mr. Cuomo’s interviews were voluntary because he lacked subpoena power in this case.

Mr. Cuomo’s report released Monday concluded that Mr. Spitzer’s communications director, Darren Dopp, and William Howard, assistant deputy for public safety, compiled and created records with the direct involvement of the acting superintendent of state police to show Bruno used state aircraft on days he attended Republican fundraisers in New York City. Messrs. Dopp and Howard planned to release the records to a reporter, the report concluded.

Neither Mr. Dopp nor Secretary to the Governor Rich Baum, mentioned in the report as receiving e-mails from Messrs. Dopp and Howard, gave testimony to the attorney general.

The letter was written the same day Mr. Spitzer, a former prosecutor, in a news conference refused to say whether it was appropriate that his top aides failed to fully cooperate with investigators looking into their use of state police against Mr. Bruno.

“I was not involved” in the decision, Mr. Spitzer said at a raucous news conference. He said he knew of the request that the aides testify. Mr. Spitzer has repeatedly denied knowing about the plot to discredit Mr. Bruno, the state’s top Republican.

On Sunday, the day before the report was issued and after the Cuomo investigation was largely completed, Messrs. Baum and Dopp submitted sworn statements through the governor’s counsel’s office.

Mr. Spitzer, the former crime-busting attorney general who made international headlines as the “Sheriff of Wall Street,” defended the decision not to provide testimony.

He said today that it wasn’t necessary for Messrs. Baum and Dopp to be questioned after Mr. Cuomo determined no crime was committed.

Mr. Baum, in an interview today, said the decision was consistent with policy.

“The Attorney General’s Office asked the counsel’s office for testimony from me, and I guess from Darren Dopp,” Mr. Baum said. “In general, the counsel’s office frowns on sworn testimony of people in the executive chamber who advise the governor because they prefer to not have wide reaching questions about the advice to the governor.”

“It was all done through counsel’s office,” Mr. Baum said.

Hours before, Mr. Spitzer was pressed in a news conference on whether refusal to testify would have been acceptable if he was still attorney general.

“As a prosecutor, I will tell you (that) you pursue facts until it’s your conclusion, unquestioned, and you reach the legal determination that needs to be made,” he said. “The attorney general reached its conclusion, and without any hesitancy or doubt, there were no violations of the law. There were judgment errors that were made that were egregious.”

Mr. Spitzer said today that the written statements by Messrs. Baum and Dopp were “sufficient for the attorney general to close its investigation.”

But the statements weren’t accepted for use in the report.

“We told the governor’s counsel’s office that we wanted to interview Darren Dopp and Richard Baum,” Cuomo spokesman Jeffrey Lerner said today. “Our investigators decided not to include the written statements as they did not have the chance to interview Dopp and Baum.”

Mr. Baum said the decision by the counsel’s office not testify isn’t in writing. He also said he doesn’t know why Mr. Howard’s interview with investigators was approved.

“The counsel’s office offered a sworn statement from me that spoke to the core accusations or the core questions being posed by the report and the sworn statement spoke to those questions,” Mr. Baum said. “And they received that and closed the investigation. That’s what I know.”

Mr. Baum said he received two e-mails from Howard and Dopp apparently regarding the political scheme, but “I didn’t respond or engage … I have no recollection of engaging.”

Mr. Baum said neither he nor Mr. Spitzer knew of the political scheme underway by Messrs. Dopp and Howard.

Mr. Spitzer also refused to comment on what he would do if subpoenaed by the Legislature to compel testimony about how much the governor knew about the political plot.

“We have not gotten there,” Mr. Spitzer said before the Ethics Commission probe was confirmed. “It is not necessary at this point.”