Leaders of the Virginia General Assembly, mired in a debate over conflict-of-interest legislation, turned today to an expert on the state Constitution for help, but came away as divided as ever.

A.E. (Dick) Howard, a University of Virginia law professor, shocked some of the legislators by questioning whether they could be prosecuted for legislative wrongdoing. "It's very hard for me to swallow that," said Sen. Clive L. DuVal (D-Fairfax).

Howard said the state Constitution's "immunity" clause generally requires the legislature to discipline its own members rather than rely on the courts to punish them. Criminal prosecution of legislators should be reserved for criminal acts committed clearly outside their legislative roles, he said.

"Serious constitutional questions" could be raised about how a proposed conflict law could apply to legislators, he said. "I cannot stand here and say the statute is constitutional."

Howard, who was an adviser to Gov. Charles S. Robb, stopped short of recommending ways for the legislature to draft revisions of the law.

After the hearing, House Speaker A.L. Philpott (D-Henry) warned again that the House may refuse to vote on the budget by its Wednesday deadline if the Senate doesn't approve a House bill to amend the conflict law.

Senate leaders remained sharply divided over what to do, with some saying the House bill unnecessarily weakens key sections of the conflict law and others insisting that the entire law was unconstitutional.

"We don't need the bill to vote on anything we want to vote on," insisted state Sen. John C. Buchanan (D-Wise), who has called the law unconstitutional. Buchanan, chairman of the General Laws Committee that is considering the House bill, said it was unlikely his committee would act before Wednesday.

"The whole bill needs to be rewritten," said Buchanan. He has said he favors a bill that would give the House and Senate power to discipline their own members except in the most serious law violations such as bribery.

"I'm not prepared yet to jump to the conclusion that a legislature cannot police itself by providing that certain kinds of conduct are criminal," said Sen. Joseph V. Gartlan Jr. (D-Fairfax), an outspoken critic of the House measure.

The legislative leaders are at odds over how to redraft the conflict law after an interpretation by the state attorney general's office that sharply restricts when legislators should vote on issues that affect their own finances.

"We need a resolution of this issue," said Philpott, making a rare appearance before a Senate committee.

The House bill reduces fines from $1,000 to $500 and eliminates jail terms for violations of key sections of the law, which became effective for legislators in 1983. The bill also would require each house to establish ethics panels to consider disciplinary action rather than referring issues to the state attorney general for prosecution.

Members of the Senate, embarrassed by the criminal conflict charges pending against Sen. Peter K. Babalas (D-Norfolk), have indicated they are unlikely to go along with the sweeping changes proposed by the House.

Babalas, the fourth ranking member of the Senate, faces criminal charges for voting to kill a interest ceiling bill and accepting $61,000 in legal fees from a now-bankrupt second mortgage company that opposed the measure.

Any changes in the ethics law would not affect Babalas, but the uncertainty over the law is likely to be raised in his defense at a trial scheduled to begin May 20, several legislators said.

Few legislators asked questions today of Howard, who served as executive director of the constitutional commission that drafted the state Constitution approved by the voters in 1970