About 250 demonstrators packed the Georgetown offices of former White House chief of staff Michael K. Deaver yesterday and left after he promised to deliver to the White House their complaints about what they called President Reagan's "massive pork barrel defense budget."

Meanwhile, the General Accounting Office is preparing to recommend that the Justice Department investigate Deaver's lobbying activities, a GAO spokeswoman told the Associated Press last night.

The spokeswoman, who spoke on condition of anonymity, said staff members decided last week that, based on their findings, the Justice Department should take over. GAO is Congress' investigative arm.

Deaver, a longtime Reagan friend turned Washington lobbyist, met with two leaders of National People's Action while members of the group chanted anti-Reagan slogans in reception areas of his eighth-floor suite. The group is a nationwide coalition of 300 social action community groups, which held a convention here during the weekend.

There were no arrests, although one demonstrator got into a brief shoving match with a receptionist.

"We went in for a meeting. We left with a victory," said Marie Bryan of Chicago, who, along with Mary Ryan of Providence, R.I., met with Deaver.

"Deaver said he will take our message and letter intact to the president and ask the president for a meeting with [group] representatives," Bryan said.

Deaver was chosen, said group spokesman Roger Kerson, "because he's very close to the president. It worked so well, we might try again," he said.

A Deaver aide, Pam Bailey, confirmed that Deaver "agreed to send the material over to the White House." But she said that "he asked that he be given the opportunity to read the material and become familiar with the group's particular issues before scheduling another meeting to discuss recommendations on whom in the administration they might meet with."

Leaders of the demonstration said the letter to the president was signed by hundreds of community leaders nationwide and charges that "over one-third ($100 billion) of your military budget is nothing more than waste and massive fraud."