Leesburg attorney John J. Moorcones, serving a 90-day prison sentence for failure to file a 1976 U.S. income tax return, was ordered suspended from the practice of law for six months last week in federal District Court in Alexandria.

"I was always short of cash," Moorcones, 42, told a special three-judge disciplinary panel during a brief hearing. "I didn't charge that much to represent people. If someone needed help, I gave it to them."

Moorcones said he had devoted considerable time to ailing family business interests in Loudoun County and estimated that of some 300 legal clients he saw in an average month, as many as half paid no fee.

District Judges Oren R. Lewis, Richard L. Williams and James C. Cacheris later agreed unanimously on the six-month suspension, effective last Dec. 4, the day after Moorcones was sentenced.

The panel rejected a proposal by Moorcones' attorney, Louis Koutoulakos, that any suspension be limited to the time served in prison. "He can't practice law in the penitentiary, so that's an idle gesture," Lewis said.

"What's wrong with it?" asked Koutoulakos.

"What's wrong with it?" Lewis retorted. "You wouldn't want to hear me say what's wrong with it--coming out of the penitentiary and being able to appear [immediately] before us."

The suspension applies only to federal court. There has been no parallel move to discipline Moorcones by the Virginia bar, Koutoulakos said.

Moorcones, who is incarcerated at the federal correctional center in Petersburg, Va., is scheduled to be released later this month.