Mayor Martin O'Malley sharply criticized the state's top federal prosecutor yesterday for what he termed a "cowardly" policy of scaling back the number of gun cases the office pursues.

The mayor shifted the blame to federal prosecutors in responding to statistics showing a significant decrease in the conviction rate in city courts for suspects charged in shootings and other felony gun crimes over the past two years.

"It's appalling in this state ... we could at the same time have the worst incidence of violence among young people and also have the only U.S. attorney's office that's doing less rather than more," the mayor said -- reviving an attack he launched in January, when U.S. Attorney Thomas M. DiBiagio said he would not prosecute as many relatively minor gun violations.

DiBiagio, who usually refrains from responding to O'Malley's public lashings, criticized the mayor yesterday for an attack he characterized as excessively political.

"The mayor's attempt to deal with disappointments, frustrations and short-term political consequences from the lethal violence in the city by lashing out only serves to alienate the law enforcement professionals who have been working tirelessly to aggressively investigate and prosecute violent crime in the city," DiBiagio said.

O'Malley, who is considering a run for governor, has staked his political career on reducing crime -- particularly the number of homicides. He acknowledged yesterday that the Police Department and state prosecutor also could do more.

The mayor said the Police Department could do a better job preparing gun cases for prosecution, and called the weak conviction rate "unforgivable."

"If we have things we can do in the Police Department regarding training, regarding motivation, regarding pay, regarding the handling of evidence -- whatever it might be -- we are 100 percent committed to making those improvements," he said.

He urged the Baltimore state's attorney's office "to make the same acknowledgement that they are not perfect and that they too need to improve. I think if they do, and that leadership can come from the top, I think we can save a lot of lives and make this city even safer than it already is."

O'Malley said DiBiagio's policy had weakened gun cases in local courts by withdrawing the threat of federal prosecution. "You should really look at how the federal government has reduced the value of plea offers in state court by their cowardly -- cowardly -- retreat from gun prosecutions," he said.

O'Malley's renewed criticisms occurred a day after The Sun published a review of felony gun cases, which found suspects in state court are less likely to be convicted and more likely to get lighter sentences than they were two years ago. Last year, the conviction rate for the state's attorney's felony gun unit was 55 percent, down from 63 percent in 2000. On average, those convicted last year were sentenced to eight years in prison, down from 11 in 2000, the data show.

Authorities say part of the problem is that police arrests have greatly increased, but not in tandem with equally strong evidence and reliable witnesses, making it difficult for prosecutors to successfully pursue the resulting influx of cases.

Police Commissioner Edward T. Norris has said he knows some of the arrests lead to weak cases, but that in the name of safety he nonetheless will continue to instruct his officers to arrest people suspected of a violent crime, even if only one witness can be found.

For years politicians have urged federal authorities to prosecute more city firearm violations in federal court. Federal prosecutors typically have a higher conviction rate than their state counterparts -- about 80 percent to 90 percent -- and violators can face lengthier federal prison terms, with no parole.

Federal prosecutors can choose which cases to try. They generally bring those with the strongest evidence, against offenders with the worst criminal histories.

Also, federal juries are drawn from across Maryland, and tend to be more conservative, more trusting of police and more likely to convict than city jurors.

Yesterday, O'Malley wasn't the only one distressed by the state court numbers. Politicians and law enforcement officials agreed that all sides -- police, prosecutors and the courts -- must figure out ways to improve the discouraging results.

Baltimore Circuit Judge Stuart R. Berger, in charge of the criminal docket and chairman of the city's Criminal Justice Coordinating Council, said judges and other law enforcement experts "need to quickly address" the data concerning conviction rates and average sentences.

City State's Attorney Patricia C. Jessamy said increased funding for her office would help improve gun prosecutions. The conviction statistics, she said, illustrate that government "can't fund one part of the system and not fund the whole."

She would like specially assigned investigators who could track down evidence and witnesses for gun cases, and more support staff for prosecutors.

She also advocated continued training of police officers in how to best gather and report evidence for trial, and suggested that a change last year in sentencing guidelines, which has resulted in much reduced sentences for gun criminals, be revisited and perhaps reversed.

State Sen. Barbara A. Hoffman, a Baltimore Democrat who heads the Senate Budget and Taxation Committee, rejected Jessamy's money argument.

Hoffman supports the police policy of increased arrests, as long as those arrests are legitimate. Now, she said, police and prosecutors must start talking. "It's known as cooperation -- to figure out what does it take to get a conviction."

DiBiagio pointed yesterday to a series of violent crime and firearm cases his office is pursuing. He is personally trying a federal firearm and drug case against Eric D. Stennett, the Baltimore man who was acquitted in state court of killing a Baltimore police officer and arrested this spring in a street corner bust.

That and other indictments show his office's commitment to making Baltimore safer, he said, adding that the victims -- and defendants -- in those cases "do not believe that we have pulled out from the city."

Sun staff writer Scott Calvert contributed to this article.