An investigative subcommittee of the Virginia Senate voted unanimously today to chastise Sen. Nathan H. Miller (R-Harrisonburg) for violating the Senate's conflict-of-interest rule, marking the first time in state history that the legislature has taken such an action.

The panel also found that Miller had not violated the state's conflict law and stopped short of seeking a formal reprimand for the 38-year-old attorney, asking only that its report be entered into the Senate's records. The subcommittee's recommendations now go to the Senate Privileges and Elections Committee, where they are considered likely to be approved later this week.

"We felt there was no intent to violate the rule," said subcommittee chairman Sen. Howard Anderson (D-Halifax.) "And we felt that the public scrutiny [Miller] has been held to over the past few months really constitutes a punishment."

At the same time, the subcommitee unanimously approved a report finding that Sen. Willard J. Moody (D-Portsmouth), the chairman of the powerful Senate Rules Committee, had violated neither the state's conflict law nor the Senate rule.

The decision of the fact-finding panel today came after more than a month of closed-door subcommittee meetings on the cases of the two senators, who had been accused of using their legislative positions to benefit the clients of their private law firms.

Miller lost the race for lieutenant governor last November amid reports that his firm had received more than $250,000 from the state's electrical cooperatives while Miller was drafting and voting for legislation that gave the co-ops $12.3 million in tax breaks and business advantages.

In a news conference late this afternoon, Miller said he felt the committee's recommendation had exonerated him, although he said that in the future he would abstain from voting on similar matters. Miller said the committee's finding that he had violated the Senate rule was "not a rebuke or anything. They just said they wouldn't have voted that way."

The panel had considered urging that stronger disciplinary action be taken against Miller, but ultimately decided against any action that would have sparked public controversy over the matter, according to a source familiar with the deliberations.

Like Miller, the 57-year-old Moody hailed the subcommittee's report as a personal victory, saying that the charges against him were the product of biased reporting by the media. "I'm very pleased with this report," said Moody. "It clearly showed that they had nothing at all to base any conflict on."

In 1977, Moody introduced a bill that would have reversed the effect of a State Supreme Court ruling against one of his legal clients. In 1979, he helped kill a bill that was opposed by a railroad workers' union that supplied his law firm with hundreds of thousands of dollars worth of business annually.