The D.C. City Council yesterday approved a bill that will give it the last word in any dispute with Statehood Convention delegates over proposed amendments to the new statehood constitution.

The bill, introduced shortly before voters approved the constitution in the Nov. 4 election, would permit a majority of council members or convention delegates to propose amendments to the constitution, subject to voter approval.

In adopting the measure yesterday, the council approved new language stating that if conflicting amendments are proposed by the council and by Statehood Convention delegates, "the amendments proposed by the Council shall take precedence and shall be placed on the ballot."

Several council members suggested during yesterday's debate that the introduction of the original bill helped improve the chances for the constitution to pass by signaling to skeptical voters that objectionable sections of the document would be amended.

Council members have said in the past that changes are needed to win congressional approval of the document.

The new language, offered by council member David A. Clarke (D-Ward 1), was approved 9 to 3, with council Chairman Arrington Dixon and council members Wilhelmina J. Rolark (D-Ward 8) and Hilda Mason (Statehood-at large) opposing it.

Mason, a delegate to the Statehood Convention and a strong supporter of the new constitution, sharply criticized Clarke's proposal. She said District voters should be the final arbiters in any disputes between the council and delegates over proposed amendments.

"I don't think we have to get into a power struggle, with our own people of the District of Columbia fighting about who has the power to amend the constitution," she said.

Under the original bill all proposals from the council and the convention would have reached the ballot and voters could choose among them. But Clarke, who also served as a convention delegate, said that approach would be too unwieldy and might foster a bitter campaign to win over voters.

"We would have almost a theater of conflict, with the council and convention going against each other," Clarke said.

During a wide-ranging 5 1/2-hour meeting yesterday, the council also tentatively approved:

* A bill permitting the District to switch by 1984 to a staggered system for registering motor vehicles, instead of the current system of issuing all new tags in March. Transportation officials and city residents testified that a staggered approach -- now used in 42 states -- would spread the workload and avoid perennial long lines of motorists registering their cars at the last moment.

* A bill requiring that children under 6 years of age be protected by seat belts or restraining seats while riding in vehicles in the District. Motorists who violate the proposed legislation could be fined $25, but a conviction would not constitute negligence, contributory negligence or any other basis for a civil action.

* A measure that would streamline the process for obtaining an alley or street closing and increase notification to affected residents. Opponents of the measure contend that it would result in a reduction in the number of public hearings held on proposed closings.