ALBANY – State lawmakers moved forward yesterday on a proposed amendment to the state constitution that would reduce significantly the governor’s budgetary powers. The action came just three weeks after legislators demonstrated they could deliver an on-time budget under the existing system.

The Senate Committee on Finance approved a resolution dealing with the proposed amendment, reporting it to the Committee on Rules and clearing the way for a floor vote in the days ahead. Passage is essentially assured.

Leaders of both the Senate and the Assembly have pressed for constitutional change as a way to end perennial late budgets, blaming the chronic problem on the excessive power they say the governor wields in constructing the annual spending plan. That argument lost its power last month when lawmakers adopted the first timely budget since 1984.

Some budget hawks have said the proposed amendment, which is now likely to go before voters in a November referendum, is more likely to stall the budget process than to accelerate it, because of a provision that invalidates executive budget bills if lawmakers fail to reach agreement on a legislative budget by a new May 1 deadline.

They say the provision removes any incentive for legislators to negotiate in good faith before the deadline, because it assures them an upper hand only after the deadline is missed. According to the provision, the backup budget that would go into effect if the deadline was missed would constitute “final action” on the governor’s budget bills and clear the way for legislative changes that are forbidden under current law.

“While this measure is being billed as an end to late budgets, it would seem instead to enshrine them in perpetuity,” the president of the watchdog Citizens Budget Commission, Diana Fortuna, said. “This seems ironic, since they just managed to pull off the first on-time budget in 21 years.”

Legislators from both houses defended the amendment, saying it contains a number of important reforms, including the controversial provision on contingency budgets. Yet Ms. Fortuna said retaining that provision ensures that all debate leading up to the referendum will revolve around it, crowding out discussion of other key proposals.

That lawmakers have opted to retain the contingency provision even after demonstrating that they could pass a budget on time has led to speculation here that the Senate and the Assembly are using the referendum as a means of cementing their independence from the executive branch as the prospect of a Democratic governor becomes increasingly likely.

According to that theory, the Republican-led Senate is looking to secure a powerful negotiating tool against the Democratic governor they expect will be elected next year, while the leader of the Democratic-led Assembly is pressing for the change as a way to maintain his role as the state’s top elected Democrat.

The state attorney general, Eliot Spitzer, is the leading candidate from either party to win the governor’s race in 2006. If he is elected, the Assembly speaker, Sheldon Silver of Manhattan, would effectively lose his voice as the chief Democratic voice on crafting the annual budget of more than $100 billion.

A spokesman for Mr. Silver, Charles Carrier, denied that such a strategy was at play in the speaker’s support for the contingency budget provision. He said constitutional change is necessary to restore the balance of power between the executive and legislative branches and that the purpose of the contingency budget provision was to cause enough discomfort to both the governor and legislators that both sides would act quickly on a resolution.

“The bottom line is that you’re exerting pressure for a conclusion,” Mr. Carrier said. “It makes everybody uncomfortable and want a resolution. We would say it’s balanced.”

For the constitution to be amended, both houses of the Legislature must pass resolutions in two consecutive sessions, and then the change must be passed by voters in a statewide referendum. Separate enabling legislation requires the governor’s approval. Governor Pataki vetoed enabling legislation on the proposed amendment last year, but the Legislature may be able to find alternative ways to implement the change.

A spokesman for Mr. Pataki, Kevin Quinn, said this year’s passage of the budget on-time suggests a change is not necessary.