Republican and Democratic party officials in Northern Virginia said yesterday they plan to request primaries on Sept. 8 to select nominees for the scheduled Nov. 3 House of Delegates elections. Several heated contest for the nominations are expected.

At the same time, those pressing legal challenges to a newly adopted redistricting plan warned that they will attempt to block preparations for the Nov. 3 election until the plan has been cleared by the Justice Department.

At a news conference yesterday, spokesman for the American Civil Liberties Union and the NAACP strongly criticized a state decision earlier this week to go ahead with planning for the Nov. 3 election saying that it amounted to a "blantant violation" of the federal Voting Rights Act.

They also charged that the state acted improperly when it used a telephone poll of General Assembly members last month to hammer out a revision to the plan. "There's just no way they can do that," said the ALCU's Judy Goldberg. "They're just daring somebody to stop them."

Both the ACLUd and the NAACP, along with more than a score of other groups, have challenged the redistricting plan on grounds that it violates federal guarantees of equal voting representation and dilutes black voting strength.

With the announcement of the plans for primaries -- rather than party conventions -- in Northern Virginia, canidates have until Aug. 7 to file their nominating petitions.

Population losses over the last decade eliminated Del. Elise B. Heinz' House seat representing Arlington and Alexandria, but Heinz has pledged to challenge Arlington's three Democratic House incumbents, Dels. James F. Almand, Mary A. Marshall and Warren G. Stambaugh, in the race for three county nominations.

In northeast Fairfax County, Republican officials say they expect up to five GOP candidates on the primary ballots with GOP incumbents Vincent F. Callahan and Martin H. Perper in a race for three nominations.

GOP officials predict that the Republican race in southweat Fairfax County will be heated, with the district's three GOP incumbents expected to face determined opposition from former state delegate Robert L. Thorburn and at least one other candidate.

Primaries are also expected to be held in Alexandria, and Loudoun and Prince William Counties.

Steven C. Yeakel, a spokesman for the state GOP, said yesterday he expects that the area's hotly contested primary contests will strengthen the party, even if they result in the defeat of an incumbent or two. "In an area where high media visibility is so important . . . the exposure gained from a primary situation is invaluable," Yeakel said. "The way we feel, the more the merrier."