Two lawsuits challenging Virginia's controversial plan for redrawing some House of Delegates election districts were filed in federal court yesterday, accusing state lawmakers of ignoring the Constitution's requirement of equal representation.

The suits, filed a day after the Virginia NAACP complained to the Justice Department that the plan discriminates against black voters, virtually assure that the state's reapportionment squabble will not be settled until at least mid-summer and possibly much later.

Many of the lawmakers who approved the plan last month acknowledged that it faced the strong possibility of rejection in the courts because it deviates radically from what the Supreme Court has said it would accept under its "one-man, one-vote" principle.

Yesterday's filings by Spotsylvania County's board of supervisors and former Virginia Common Cause chairman Albert L. Ely both charged that the reapportionment plan violates the 14th Amendment and asked that a new plan be drawn. Similar suits are being prepared by the American Civil Liberties Union, Common Cause and others.

"It was like putting the fox in the henhouse to ask the General Assembly to redistrict," said retiring Republican Del. Raymond R. Robrecht, who is acting as Ely's attorney in the suit filed in Roanoke. "Having been through it one timne, I can say it was pretty absurd."

The Spotsylvania suit, filed in Richmond, claimed that the plan grants residents of the fast-growing county only 72 percent of the voting representation to which they are entitled, and said it deviates by more than 55 percent statewide from the ideal election district size dictated by 1980 census figures.

In a 1971 Virginia reapportionment case, the Supreme Court held that variances in excess of 16 percent would seriously jeopardize equal representation and were therfore not acceptable.

Calculations used by the lawmakers show the current plan's variance at 26 percent, but Spotsylvania officials said that figure is unrealistically low because it does not account for "floater" seats that are spread among several House districts.

If the court finds the plan to be unconstitutional, federal judges are empowered to impose their own reapportionment plan. They may also order the General Assembly to return to Richmond for more work on the embattled plan, which was approved last month after weeks of stormy debate.

Many state lawmakers have said privately they hope the courts will return the plan to them, fearing that a court-drawn plan would eliminate multi-member districts and thus endanger many incumbents.

NAACP officials earlier this week asked the Justice Department to reject the House reapportionment plan, claiming it dilutes the voting strength of blacks and urging that a single-member district plan be instituted in its place.

"We're very opposed to the deviation in this plan, which was created solely because they drew the lines in such a way as to dilute black representation," Jack Gravely, state NAACP executive secretary, said yesterday.

"There is only one political party in the state of Virginia -- the conservative political party. And I think the only real interest they have is keeping blacks, women and liberals out of the political arena in any significant numbers," he said.

Under the federal Voting Rights Act, the Justice Department must review Virginia's legislative and congressional redistricting plans to assure that minorities are treated fairly.

The Justice Department has until late June to make its decision, and it is considered unlikely that the courts will address the case until Justice has completed its review. Primaries are set for Sept. 8 and the general election is scheduled for Nov. 3.