Maryland U.S. Attorney Thomas M. DiBiagio received an unusual written admonishment yesterday from superiors who ordered him not to bring new public corruption cases without their prior approval.

Officials in Washington said Deputy Attorney General James B. Comey also telephoned DiBiagio to convey displeasure with a memo in which DiBiagio urged his prosecutors to produce three "front-page" indictments by Nov. 6, four days after the presidential election.

DiBiagio, a Republican appointee, was advised by others in the Justice Department's Washington headquarters to make no effort to learn who leaked the memo and other internal documents that led to yesterday's action, the officials said.

In a letter the department released to reporters, Comey told DiBiagio that he was taking the action in order to protect the "credibility" of the office. DiBiagio was "directed, until further notice, to submit to me for review any proposed indictment in a public corruption matter. You may not bring such a case without my personal approval."

The unusual rebuke, which a former Maryland U.S. attorney described as a "slam," fueled speculation in legal circles over DiBiagio's prospects for appointment to a second term. The prosecutor has at times seemed at odds with superiors at the Department of Justice, crusading against corruption when law enforcement's declared top priority was terrorism.

Shortly after he was appointed to a four-year term by President Bush in 2001, DiBiagio said he would emphasize prosecution of white-collar crime and public corruption in the state, which has long been under Democratic control.

Although he successfully prosecuted the superintendent of the state police and currently is trying an investment banker who handled millions in state funds, DiBiagio has not brought charges against any elected official.

His office is conducting a probe of Baltimore's City Council, whose 19 members are all Democrats, and has sought documents detailing an array of financial practices.

In the letter, Comey said he had reviewed the internal documents from DiBiagio's office -- an agenda for a May staff meeting and two e-mails he sent to his prosecutors. The documents were obtained by the Baltimore Sun and were the subject of a report in the paper's Thursday's editions.

The agenda set out several goals to be accomplished by Nov. 6. Among them were improving relations with the FBI and obtaining "Three 'Front-Page' White Collar/Public Corruption Indictments," the Sun reported.

In an e-mail to prosecutors July 1, DiBiagio described a municipal corruption indictment in Philadelphia. "Why aren't we doing cases like this," he wrote in the e-mail quoted in the Sun. "Am I the only one embarrassed by the fact that this Office has not convicted an elected official of corruption since 1988?"

Two days later, he wrote again, saying that the earlier e-mail had sent the wrong message and explaining that he was frustrated and had hoped to move faster.

The chairman of the Maryland Democratic Party, Isiah Leggett, called for DiBiagio's resignation Thursday after the documents were disclosed. Leggett said the prosecutor had used his office "as a political weapon to indict innocent people for political gain."

Several prominent defense lawyers and former federal prosecutors have defended DiBiagio, saying the documents simply underscore his long-held passion for combating public corruption.

Comey told DiBiagio that his "intentions may not have been accurately reflected" in the documents but said, "We can never allow political considerations -- or the perception of such considerations -- to taint the work done by our dedicated investigators and prosecutors."

DiBiagio declined to be interviewed yesterday. In a statement, he acknowledged receiving the letter and said he would comply. "I regret sending any improper message with regard to the investigation of public corruption matters," he said.

If Bush is reelected, he will decide whether DiBiagio is reappointed, though presidents frequently defer to the judgment of the top elected official of their party in the state -- in this case, Gov. Robert L. Ehrlich Jr. (R). Ehrlich's spokesman said the governor would not comment on the controversy.

DiBiagio's combative style has ruffled feathers at the Justice Department in the past. In 2002, he wrote a memo, which surfaced publicly, strongly criticizing the FBI's Baltimore field office for failing to pursue white-collar crime investigations. He clashed repeatedly with Gary Bald, now a senior FBI counterterrorism official in Washington, when Bald was the special agent in charge in Maryland.

One of DiBiagio's predecessors, Stephen H. Sachs, said yesterday that the e-mails were "a woefully inartful and stupid way of expressing his desire to do as much as he can to establish his legacy."

"I think he saw the end is near," said Sachs, a Democrat. "One way or another, I think Tom saw that the election was going to mark a passage for him. In view of today's development, it would be much more likely that [DiBiagio's superiors] would want to make a change. They've now said to the U.S. attorney that you are on a short leash."

Mark Corallo, a spokesman for the Department of Justice, called DiBiagio "an excellent U.S. attorney," saying: "His office has done stellar work. This is an unfortunate incident, and I think the deputy attorney general handled it with this letter."

Corallo, who described the letter as "a disciplinary action basically," declined to comment on DiBiagio's prospects for a second term.

Staff writer Susan Schmidt contributed to this report.

Thomas M. DiBiagio wanted "front-page indictments" obtained by Nov. 6.