The mayor and City Council speaker’s power over the budget process would be weakened and dispersed among committees under a proposal being floated by Council Member David Yassky of Brooklyn.

The plan calls for the budget to be broken into individual line items by the Independent Budget Office, a nonpartisan city agency that analyzes the city’s finances, instead of by the mayor, and for Council committees to vote separately on city agencies’ budgets before approving the overall budget.

Mayor Bloomberg released a $58.5 billion preliminary budget last month, which is the starting point for negotiations between the mayor and City Council. The final budget will be approved in June.

Under current procedures, Council members speak out on the budget in hearings but vote only on a final agreement negotiated between the mayor and the Council Speaker. They are barred from approving individual budget items or agencies’ spending. Mr. Yassky’s plan would shift power to council committees. For example, the Council’s Public Safety committee would vote on the police department’s preliminary budget and the Environmental committee would approve the budget of the city’s environmental protection agency. Because the Council is required to submit a balanced budget, Council members would not be able to increase overall spending, but the committees could rearrange which programs receive funds within the agencies, giving them more freedom to tinker with the mayor’s proposed priorities.

“It’s hard to believe that of the $59 billion city budget, the City Council would make the same exact trade-offs that the mayor makes,” Mr. Yassky, a candidate for city comptroller, said. “The fact that you don’t see the Council substituting some of its trade-offs for ones that the mayor has made says that the process is not working as best as it should.”

Mr. Yassky said that his plan would encourage greater fiscal discipline among Council members by asking them to determine which programs are winners and which could be eliminated or reduced. “Forcing people to confront those trade-offs would force Council members to look much harder for ways to cut spending,” he said.

City Council Speaker Christine Quinn has already pressed the mayor to provide more specific agency budgets in the past, as Mr. Yassky calls for, and with some success. In October she announced that this year’s budget would contain numbers broken down by program from some sixteen agencies, up from two agencies the previous year. Mr. Yassky praised Ms. Quinn’s changes as “huge progress,” but said that it should be a jumping off point for granting more influence to the Council committees, who would use the information to debate the city spending in detail.

It is unclear how much of Mr. Yassky’s plan could be achieved through internal Council rule changes and whether they would garner widespread support. Part of his plan includes giving the IBO’s revenue estimates the force of law rather than the mayor’s estimates, which some say may require a voter referendum.

Council member Tony Avella of Queens said yesterday that while he believes the speaker exercises too much control over the budget, he is skeptical of the plan’s viability. “The speaker has all the power,” Mr. Avella said. “Giving more power to the committees is something I’ve called for a long time, but I don’t know if you can translate the budget into that.” He suggested letting the Council veto individual items in the budget instead of voting only on the whole package might distribute power more equitably.