Mayor Marion Barry said yesterday that an increase in the city's property tax rate would be necessary this year if property assessments do not rise sufficiently to meet increased demands for revenue in his proposed budget for fiscal 1984.

Barry, interviewed in his office one day after unveiling a hold-the-line $1.9 billion budget for the coming year, indicated that a rate increase of 4 to 7 percent might be necessary if the rate of inflation runs ahead of the increase in property assessments for the coming year, as city budget experts are now predicting.

It was the closest that Barry, who has repeatedly pledged not to increase major taxes, has come to reversing himself on the issue. He said, however, that since any increase would be accompanied by little or no rise in assessments, the impact on D.C. property owners would be slight.

"Once we get the final assessments we'll see if it's sufficient growth" to meet revenue demands, Barry said. "If it's not, the impact of a rate increase won't be significant."

On a house valued at $100,000, assuming the assessment remained stable, a 4 percent increase in the tax rate would equal a $45 increase in taxes.

Barry's proposed budget already hinges on City Council approval of a wide range of increases in lesser taxes and fees totaling about $26 million. He did not indicate whether a property tax increase would fall on homeowners, businesses, owners of apartment buildings, or all three classes.

Council member John A. Wilson (D-Ward 2), chairman of the Finance and Revenue Committee, said he would not rule out council approval of either the mayor's tax package or an increase in the property tax rate.

"Given the situation, I would have attached a larger tax package to the budget," Wilson said in an interview. "I don't think that by politically avoiding a realistic tax increase that we're doing the citizens of the city a favor."

He added, "People should understand we're in austere times and what we don't pay for now, we'll pay for eventually."

While the mayor's budget is certain to stir controversy over proposed cutbacks in social services and the absence of funds to help retire the city's long-term debt, most City Council members spent much of a meeting yesterday arguing about the way the mayor released the budget.

Several members, including some of the mayor's strongest supporters, loudly complained they had not been briefed on the budget before Barry released copies of it to the press. When Barry tried to placate them by offering to brief them privately today, most council members turned him down and voted to ask him to appear in the council chambers on Thursday to explain the budget.

"I have a serious problem with a private budget briefing," said Hilda Mason (Statehood-At large). "We are doing public business with public money. I won't attend."

"I feel that this is an outrageous situation," said council member Polly Shackleton (D-Ward 3), one of the mayor's staunchest allies. "The council is not given the information until everyone else has it."

Council member Jerry A. Moore Jr. (R-At large), not often given to anger, scolded Barry and said, "I think he's misguided right now."

Barry, who plans to be in Atlanta Thursday for the observance of Martin Luther King Jr.'s birthday, brushed aside the council members' complaints, which he called "theatrics."

Council Chairman David A. Clarke, who was given a sneak preview of the budget by the mayor's office, said yesterday he has "serious questions" about Barry's proposal to eliminate the general public assistance program, which provides aid to persons temporarily out of work because of illness or disability.

Clarke said the budget "appears to take money out of programs and puts it into staff" and other administrative costs, which would enable Barry to keep a campaign pledge not to lay off any full-time city employes. "But then you've got no programs," Clarke said.

Joslyn Williams, president of the Metropolitan Washington Council AFL-CIO, said yesterday he was disappointed by the depth of cuts in social services that Barry has proposed.

"I really think the Barry administration must have taken its cue from Ronald Reagan," Williams said. "It seems to me that there always are alternatives besides taking it out of the hides of people who need it most."

Barry said yesterday that it was "excruciating and painful" to draft his new budget at a time of pressing demands for city services amid declining revenues, and defended his decision not to include $20 million to help retire the city's long-term debt.

He said he told Rep. Julian C. Dixon (D-Calif.), chairman of the House appropriations subcommitteee on the District of Columbia, of his decision to omit the funds and that "He understood the problem."

"A lot of cities are adding to the deficit," Barry said. "I'm not adding to it."

Barry said the city's financial situation is better than it was three years ago, and that he did not anticipate the city would have trouble entering the private bond market for the first time later this year.