The Justice Department today rejected an unprecedented claim by a group of white politicans who charged that Richmond's black city council majority violated the Voting Rights Act by redrawing political wards here in a manner that virtually assures continued black domination of the city government for the next decade.

The decision was a major victory for Mayor Henry L. Marsh III, a black Democrat, who personally redrew the lines for Richmond's nine council districts. Opponents, including the city's four white council members, attacked the plan, saying it guarantees blacks will retain their 5-to-4 council majority.

The Reagan administration's support for the plan was a blow to a group of whites, many of them conservative Republicans, who had organized what is believed to have been the first effort by whites to invoke the Voting Rights Act in claiming "reverse" racial discrimination. Their effort to sway Justice included a letter-writing campaign that flooded the department with nearly 3,000 protest letters and a meeting 10 days ago between department officials and more than two dozen white civic leaders, including two of Virginia's most prominent GOP fund-raisers.

Assistant Attorney General W. Bradford Reynolds of the department's civil rights division, agreed today with their argument that the Voting Rights Act applies equally to all cases of discrimination, whether against blacks or whites. But Reynolds maintained the Marsh-designed plan was drawn "in a conscientious and fair manner," accurately reflecting growth in the city's black population during the past decade.

An alternative plan offered by the white council members "would have resulted in significant retrogression in the opportunities of black voters" in one council ward, Reynolds said in a letter to Richmond officials.

Separately, the Justice Department also announced yesterday it was approving a congressional redistricting plan approved this spring by the Virginia General Assembly. The plan was the first of three redistricting plans drawn by the Virginia state legislature to win immediate approval from the department. Justice earlier rejected initial versions of redistricting plans for the two houses of the legislature on grounds they diluted the strength of black voters in the state.

Responding to rejection of the white politicians' challenge to the city council districting, Councilman William J. Leidinger, Mayor Marsh's principal antagonist, called it "a bone-crushing disappointment in terms of fair play. There's no question that if it stands, the present majority will be in control at least until May, 1982." Leidinger had led a delegation of whites to Washington.

Marsh said today he was pleased with the decision of the department, which under the Voting Rights Act must review all election law changes in Virginia to ensure any changes are not racially discriminatory. The mayor accused the city's white minority of attempting to subvert the intent of the 1965 law, which was designed to protect the rights of racial minorities in the South whose efforts to vote had been restricted by many states.

"It was an attempt to politicize the process and convert a legal issue into a political one," said Marsh, who suggested the whites had hoped to draw conservative partisans from the Reagan White House into the fight.

The mayor said the white alternative redistricting plan, which Leidinger said would have created a 4-to-4 split with one "swing" district, would have led to a white councilmanic majority.

"It takes a lot of nerve to ask the Justice Department to participate in that kind of deal," Marsh told reporters after his session with department officials last week. "I guess they aren't short on nerve."

The struggle over redistricting is the latest battle in the ongoing political warfare between Richmond's white and black power brokers over who will control this city of 219,000, where black population during the 1970s jumped from 42 percent to 52 percent. Blacks took control of the city council here -- and the council then chose Marsh as the city's first black mayor -- in 1977 after Justice ordered the city's at-large electoral system scrapped and a ward system instituted.

White council members made an all-out effort but failed to capture the city's so-called swing ward south of the James River in last year's elections. That retained the 5-to-4 black majority and gave Marsh an opportunity to redraw five districts with no less than 68 percent black majorities. Two of the present white councilmen were placed in the same district.

Marsh has contended he drew the wards without paying any attention to race. "With all due respect to Henry, that's just a plain lie," said former councilman Henry Valentine II, a Richmond stockbroker who joined the opponents in their journey to Washington. Valentine is one of GOP gubernatorial candidate J. Marshall Coleman's chief fund-raisers and an ardent supporter of President Reagan.

Valentine acknowledged some irony in his group's attempt to invoke the Voting Rights Act, which he and many other white conservatives bitterly oppose. "What's sauce for the goose is sauce for the gander. . . if we've got to play by those rules, so should the blacks."

In searching for leverage over the black council majority, the four white members earlier this year blocked passage of a city bond ordinance for nearly $34 million in improvements. The money includes $6.5 million for the city's aged school system and $2 million to help rebuild the Main Street Train Station, a turn-of-the-century Victorian landmark.

The action has infuriated black leaders who see it as an attempt at blackmail. "There are some people who'd rather see this city run into the ground then under black leadership," said Councilman Henry Richardson.

Some whites have also taken strong exception to the delay. "The white minority is just not playing fair with the people of this city when they hold the capital budget ransom," said the Rev. Benjamin Campbell of the nonprofit Richmond Urban Institute.

Campbell says the ongoing power struggle has damaged not only racial harmony but also the morale of city residents. Noting that a federal grant for the train station project will expire in November without matching money from the city, Campbell says "It seems every time a decent project comes up it gets caught up in this warfare and gets killed."

Leidinger, whose major complaint about Marsh is that he has usurped powers normally reserved to the council and the city manager, said his group will now consider challenging the redistricting plan in federal court.

But Marsh and his supporters doubt a court test would succeed. "This was a game of pure political arithmetic and we've got the marbles," said black councilwoman Willie Dell. "The other side just isn't willing to concede the game is over."