The chairman of the D.C. City Council's finance committee said yesterday that Mayor Marion Barry and his top aides had "deceived the council" by not fully disclosing the availability of $7.7 million in federal discretionary funds that could have been used to offset city budget cuts.

"Let's not argue whether this is a deception, because it's absolute deception," Council Member John A. Wilson (D-Ward 2) told Barry's budget director, Gladys W. Mack, during a tense exchange as Mack appeared before the council's Finance and Revenue Committee.

The fund in question are given to the District each year by the federal government to compensate for costs incurred in administration federal grant programs, Unlike most federal funds received by the city, these monies have no strings attached. Although they are supposed to be used to augment the grant programs, technically the District government can spend the funds any way it chooses, and the money is generally used as a kind of discretionary fund.

The District received a total of $9.2 million in such funds for the current fiscal year, which ends Tuesday. Around $1.5 million went to the D.C. school system, leaving $7.7 million in the control of the mayor and various city agencies.

Wilson complained that Barry and his aides never made it clear to the council that these funds were available, even as the city's budget crisis forced layoffs of city workers and severe cutbacks in services.

"You spend without telling us, you hide it all over, and then you tell us, "Well, it's in the budget, find it," Wilson told Mack. "What are we playing, finders-keepers? Who do you think I am, Houdini or something?"

The city's 1980 budget, approved last year by the council, reflected the existence of the funds. But they were listed under four separate categories and under various departments, and Wilson charged that Barry and his aides warned the council that like other federal monies, the funds could not be tampered with.

Mack gave the committee a report on how $2 million of the money directly under the mayor's control was spent, but she was unable to say how the remaining $5.7 million was used by the various city departments that had control of the funds. Mack promised to return with a report showing the disposition all the money.

"It's a slush fund for the mayor and a slush fund for the agencies," said Betty Ann Kane (D-At Large), a member of the committe. "When there's a situation like the budget crises this year, having that money sitting there is just shocking."

Mack said the money was used to pay unfunded expenses. She said, for example, that $50,000 went to the Board of Elections and Ethics to defray the cost of printing ballots, and more than $128,000 went to set up a new employee appeal board, for which Congress had denied funding.

More than $100,000 went to pay salaries in Mack's own Office of Budget and Resource Development. More than $280,000 went to Barry's own office. A total of $307,000 went to the office of City Adminstrator Eligjah B. Rogers. The figures provided by Mack indicated that most of the money went to pay salaries.

Legislation passed earlier this year will give the council authority over such expenditures in the future. "Maybe we'll find out how so many people get paid in this goverment without having it reflected in the budget," Wilson said.

Mack said that the budget for the 1981 fiscal year, which begins next Wednesday, provides that Barry will have ruoughly the same amount in discretionary federal monies -- around $2 million under his direct control -- that he had in the current year.