Senatorial candidate Andrew P. Miller called on Virginia Democrats yesterday to unite to "rescue" the state from what he called "the embarrassment of the past six years" - representation by retiring republican Sen. William L. Scott.

In his strongest speech to date is his campaign for Scott's U.S. Senate, seat, the usually low-key Miller lashed out at his republican opponent, John W. Warner, as "Bill Scott's country cousin" and said Virginia deserves better representation than that in the years ahead.

Miller appeared with former lieutentant governor Henry E. Howell at an outdoor reception in Fairfax County and said he welcomed Howell's support in the current campaign.

"What this campaign is all about," Miller said, "is whether we will have a senator you can be proud of . . . who will listen to you, or, like the incumbent, slam the door in your face . . .

"Whether we will have a senator who has an open mind toward the issues of our time rather than . . . a kneejerk reaction."

Miller said such issues as our relationship with the Soviets, strategic arms limitation, and keeping the nation a strong partner in the world's economy "are matters for which there are no knee-jerk solutions."

"These are matters," he said, "which require the best thinking of all Virginians.

The current campaign, he said, is a "watershed" when Virginias must ask themselves "whether Virginia will once again speak for the nation . . .

"It's about whether you have a United States senator who believes in the principle that we recognize here in Virginia; a standard of integrity in public life, or whether you have somebody who sends out the type of trash that's going through the mail these days' on behalf of Warner's campaign.

Miller spoke at a $25 a-person fundraising brunch at the McLean home of State Sen. Clive L. DaVal II - an event killed as a show of unity for the often fractions elements of the state Democratic party.

Among those appearing with Miller were former lieutenant govennor Henry E. Howell of Norfolk, who defeated Miller in the party's gubernatorial primary last year, as well as formet Fairfax supervisors Rufus Phillips and Fred Babson, and former delegate Carrington Williams of Fairfax, who with DuVal opposed Miller for this year's senatorial nomination.

Several local Democrats said the party togetherness was especially important in light of Miller's strategic campaign decision - which came to light last week - not to schedule appearances by the sometimes divisive Howell as part of the Miller campaign.

Miller said he was "mighty proud" that Howell was able to leave Tidewater in time "to be with us here today" and "end the divisive rumors and halftruths which have been circulating about Democratic disunity this fall."

Miller said "Andy Miller is his own man" and "Henry Howell is his own man" and "the two of us have differences from time to time . . . "But we both support the Democratic candidates, and neither one of us wants John Warner in the United States Senate."

I'm here today to say I welcome Henry Howell's support just as I welcome the support of . . . Virginians across the state" from conservative Virginia House Speaker John Warren Cooke of Mathews to Northern Virginia Reps. Herbert Harris and Joseph Fisher.

Miller staffers said the fund-raiser signaled no change in the decision to keep Howell's role in the campaign low-key, but there was much applause for the former lieutenant governor, who Williams said "holds out his hand to heal the wounds of the Democratic Party."

"I come here to witness for unity . . ." Howell shouted to the 200 or so applauding faithful gathered under a locust tree in DuVal's backyard. "I'm enthusiastic about this election.

"I want Andy to win. And I want the word to go out to all those in doubt that there's only one way to provide leadership for Virginia in the U.S. Senate and that's to cast a vote for Andy Miller."