While an angry audience catcalled and hissed, Virginia's Democratic-controlled legislature today launched its investigation into reports that Republican lieutenant governor candidate Nathan H. Miller had helped secure passage of legislation that benefited his law firm's clients.

Democrats called the meeting in the General Assembly building "perhaps unprecedented," and "a very, very sad task." Republicans labeled it a "kangaroo court," and "one of the sorriest and most contemptible days" of the legislature. Before the meeting, the candidate's father, Garland Miller, carried a picket sign reading, "Stop This Nonsense."

"I don't like people being smeared," he said.

In the end, the powerful Senate Rules Committee appointed a panel to look into reports that Miller had twice drafted and voted for legislation that would give financial advantages to his law firm's clients. The panel is also to review the state's conflict-of-interest laws.

The meeting marked the first time in at least 100 years that the Virginia legislature has begun a formal probe of one of its members. Apparently heeding admonitions from Democratic gubernatorial candidate Charles S. Robb to avoid the appearance of partisanship, Democratic committee members agreed that the panel will not meet formally until after the Nov. 3 election.

"I would not want it to be said that this committee was politically motivated," said its chairman, Sen. Willard Moody (D-Portsmouth). The remark prompted loud, derisive laughter from an audience of almost 200 people, most of them Miller supporters. But committee members made it clear that the delay was not to be interpreted as a vindication for Miller.

"After the first article appeared, members of this committee chose, because of the nature of the campaign, to remain silent," said Sen. Hunter B. Andrews (D-Hampton), Senate majority leader. "Regrettably, the candidate stated that we had in effect condoned his action because we remained silent."

Pro-Miller protesters in the audience, many of whom had been supplied with protest signs by Miller's campaign headquarters, repeatedly called out insults to the committee, which is dominated 14 to 1 by Democrats. Their excitement rose to a peak with an unsuccessful attempt by Sen. Ray L. Garland (R-Roanoke) to gain the committee's ear.

"Will you open this committee up to examine conflict-of-interest charges against every member of the General Assembly?" he cried dramatically, waving a file folder that he said contained information on conflicts of interest by "various members" of the legislature.

Chairman Moody, who has himself been accused of conflict of interest in the past and who recently contributed $500 to Miller's Democratic opponent, pounded the gavel repeatedly for order as the crowd cheered. "We're here to carry this forward without stage acting," he snapped, cutting off Garland.

The Washington Post this week reported that Miller, a Shenandoah Valley lawyer, introduced legislation that could allow a longtime client of his law firm to more easily build a court case for recovery of potentially valuable mineral rights.

Earlier, The Post reported that Miller had accepted at least $250,000 in legal fees while drafting and voting on legislation that gained $13.2 million in tax breaks and business advantages for other legal clients of his firm, the state's electrical cooperatives.

Miller did not refute the specific details of this week's report on the mineral rights law, but said he had introduced the bill in an attempt to benefit many people, "some of them clients and some of them constituents."

State Republican Chairman Alfred Cramer III yesterday attacked the rules committee probe as a "witch hunt," but most GOP officials have fallen short of defending Miller personally. Appearing in Alexandria's Old Town today, GOP gubernatorial candidate J. Marshall Coleman said, "I support Mr. Miller," but declined to discuss the substance of the reports about his running mate.

Miller, campaigning in Norfolk, did not appear before the committee today because "we don't want to lend credibility to a charade," said Ralph Wunder, the candidate's press secretary. Wunder would not say whether Miller had agreed to testify when the subcommittee does meet. "He hasn't been invited, and we're certainly not going to offer," he said.

Sen. Wiley F. Mitchell Jr. (R-Alexandria), who came to the committee as Miller's representative, said after the meeting that Miller "approved" of the inquiry, but added, "If I were a member of the committee, I would be very reluctant to change the rules in the middle of the game."

Several members of the rules panel expressed the hope that the Miller episode will prompt a redrafting of the state's regulations regarding conflict of interest. Presently, senators are instructed not to vote on matters in which they have an "immediate, private or personal interest," but there are no set enforcement procedures.

"Conflict of interest, in my judgment, has always been a matter for a man's conscience," said Sen. Edward E. Willey (D-Richmond), the senior member of the Senate. "The time has come that we're going to have to write some regulations to define what you can and can't do.