The union that represents District police officers, critical of the sentence given a 19-year-old Northeast Washington man convicted of murdering a police officer, said yesterday it will lobby city officials to toughen sentences in such cases.

"You hold the life of a police officer at a shamefully low price," Gary Hankins, chairman of the local Fraternal Order of Police's labor committee, said in a letter yesterday to Superior Court Judge George H. Revercomb. "This kind of sentence demeans Gary and my fellow officers."

On Monday, Revercomb sentenced Mark Anthony Watson to life in prison for the slaying of officer Donald (Gary) Lunning on Sept. 14, 1982. Except in rare cases, D.C. law mandates a life sentence for first degree murder, with eligibility for parole after 20 years.

Watson, of the 1200 block of G Street NE, was convicted June 13 of first degree murder, assault on a police officer, carrying a pistol without a license, receiving stolen property and unauthorized use of a car. The FOP criticized Revercomb for ordering that Watson's sentence for the lesser offenses be served concurrent with, rather than consecutive to, the life sentence.

Watson could have faced at least 25 years in prison for the lesser charges, in addition to the life sentence.

"I don't think 20 years in prison can be considered a low sentence," said Stephanie Duncan-Peters, Watson's attorney. The judge refused her request that he sentence Watson under the federal Youth Corrections Act, which in such cases recommends a maximum sentence of life -- with no minimum time to be served -- for eligible youths under 22.

Revercomb declined to comment on the case yesterday.

Hankins said the FOP will ask Mayor Marion Barry and the City Council to toughen the penalty for the murder of a police officer, a corrections officer or a firefighter to life in prison with no chance of parole. He said the union will also press Barry and the council to increase the penalty for murder of a civilian during the commission of a felony to a mandatory life sentence.

Luning, whose death helped prompt the drive to equip all D.C. police officers with bulletproof vests, was shot once in the chest in what the FOP called an "execution."

Watson's lawyer acknowledged in court that her client shot Luning, but said Watson did so in self-defense and that Luning, who was in plain clothes at the time, had failed to identify himself as a police officer.

At Yesterday's FOP press conference, Luning's widow expressed support for the union's lobbying drive.

"I was devastated," Jodie Luning said of her reaction to the sentence. "Anybody can go kill a cop anytime they want to," she said. "I feel there's no justice at all."