A bill that would permit Washington voters to force public referendums on controversial legislation -- possibly starting as soon as November -- won preliminary approval yesterday from the D.C. City Council.

Opponents of the $99 million downtown convention center and supporters of legalized gambling promptly announced that they intend to use the new mechanism to put those issues on the ballot of the Nov. 6 school board election.

Enactment of the measure into law requires a second council vote, scheduled for March 27.

Foes of the convention center had hoped to force a referendum at a special election to fill two council seats on May 1. But their petition was rejected by the D.C. Court of Appeals because the bill being enacted was not yet law.

Backers of gambling sought an advisory referendum on their proposal May 1, but those hopes were dashed yesterday when council sponsor David A. Clarke (D-Ward 1) announced that he lacked the votes to force action. Passage of a council resolution had been sought.

As first considered yesterday, the referendum authorization would have contained a timetable too tight to permit any referendum next November, council members said.

So the council voted, 7 to 5, to approve an amendment offered by Hilda Mason (Statehood-At-Large) to shortcut some procedures for those wanting to get issues on the November ballot.

The later approval of the measure was unanimous.

The vote was a victory for the Convention Center Referendum Committee, which had pushed for the amendment and whose leaders were jubiland. The action would validate petitions containing 12,500 signatures already collected that seek a public vote.

The committee contends the center would be a financial loser for the city, a view sharply contested by planners, business leaders and organized labor, who see it as a spark plug for development and an expanding convention industry.

Mayor Marion Barry told reporters he opposes a referendum on the project, and that he would not suspend land acquisition or other preliminary work pending a referendum.

City voters approved the adoption of initiative, referendum and recall procedures at the November 1977 election, and Congress later ratified that action. It then was up to the council to adopt legislation creating the machinery for such votes.

Police Chief Burtell Jefferson told the council that disability retirements in his department so far this fiscal year have dropped to 24 percent of the total. Barry told Congress last week that combined disability retirements of police and firefighters in the 1978 calendar year had totaled 44 percent.