District of Columbia residents can expect greater tax increases than previously expected next year as a result of an every-growing gap between revenues and the rising city budget, the chairman of the D.C. City Council's Finance and Revenue Committee forecast yesterday.

"There is no need of us kidding ourselves any longer. We've got hard decisions to make -- really hard decisions," John A. Wilson (D-Ward 2) declared at a hearing by his committee into the just-disclosed cash shortfall that threatens to force a $28 million cut in city spending between now and Sept. 30.

City Administrator Elijah B. Rogers directed agency heads last week to propose ways to cut that amount out of their budgets. Budget director Gladys Mack, yesterday's main witness, said about two-thirds of the officials have complied so far.

Mayor Marion Barry warned last August that the city would have to find at least $66.7 million to finance higher costs in the budget he expects to submit for the 1982 fiscal year, which begins Oct. 1, 1981. He declared at that time that sharp tax increases would be needed.

Wilson predicted yesterday that the gap between revenues and costs in 1982 actually would reach $145 million, rising to $254 million by 1984. These figures are conservative, Wilson declared, and assume that Congress will not increase that annual federal payment to the city -- now authorized at a maximum of $300 million.

President Carter, in the 1981 federal budget he submitted to Congress this week, proposed the adoption of a formula for setting the federal payment that would produce an estimated $320 million for the city in 1982. Barry has said this is not enough.

Yesterday Wilson ticked off a list of eight possible tax increases -- including a 5 percent increase surcharge on the personal income tax -- that altogether would raise only $78.9 million. Wilson did not advocate these increases, but cited them as illustrating the scope of the problem.

Within the council, Wilson's committee would consider any tax-raising legislation.

Wilson said he would propose legislation to create a joint task force of council and mayoral representatives to explore options in the city's finanical future.